September 2006
Three Cisco Security Advisories
ID: 00640
Ref: 613/2006
Date: 21 September 2006:14:07:21
Version: 1
Title: Three Cisco Security Advisories
Abstract:
Vendors affected: Cisco
Operating systems affected: Cisco
Applications affected: Cisco
Title
=====
Three Cisco Security Advisories:
1. cisco-sa-20060920-docsis - DOCSIS Read-Write Community String Enabled
in Non-DOCSIS Platforms
2. cisco-sa-20060920-ips - Cisco Intrusion Prevention System Management
Interface Denial of Service and Fragmented Packet Evasion Vulnerabilities
3. cisco-sa-20060920-guardxss - Cisco Guard Enables Cross Site Scripting
Detail
======
1. A vulnerability exists in certain Cisco IOS software release trains
running on the Cisco IAD2400 series, 1900 Series Mobile Wireless Edge
Routers and Cisco VG224 Analog Phone Gateways. Vulnerable versions may
contain a default hard-coded Simple Network Management Protocol (SNMP)
community string when SNMP is enabled on the device. The default
community string is a result of inadvertently identifying these devices
as supporting Data Over Cable Service Interface Specification (DOCSIS)
compliant interfaces. The consequence of this error is that an
additional read-write community string may be enabled if the device is
configured for SNMP management, allowing a knowledgeable attacker the
potential to gain privileged access to the device.
2. The web administration interface of Cisco IPS/IDS devices contains a
denial of service vulnerability. It is possible to send a malformed
SSLv2 Client Hello packet to the IPS/IDS web administration interface,
which may cause the process (mainApp) responsible for managing remote
access to fail. This results in an IPS/IDS device becoming unresponsive
to all future remote management requests through the web administration
interface or the command-line interface (CLI) via SSH and the console.
This vulnerability is documented in Cisco bug IDs CSCsd91720 and
CSCsd92033. This vulnerability was originally fixed in Cisco IPS
version 5.1(2).
3. The Cisco Guard DDoS Mitigation Appliance is a distributed
denial-of-service (DDoS) protection system. Malicious DOS traffic is
identified with a Cisco Detector and diverted to the Guard for attack
mitigation. Under normal circumstances, the Guard plays no role in
valid traffic; it is specifically designed to deal with large volumes
of invalid traffic.
1.
- -----BEGIN PGP SIGNED MESSAGE-----
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Cisco Security Advisory:
DOCSIS Read-Write Community String Enabled in Non-DOCSIS Platforms
Document ID: 71255
Advisory ID: cisco-sa-20060920-docsis
http://www.cisco.com/warp/public/707/cisco-sa-20060920-docsis.shtml
Revision 1.0
For Public Release 2006 September 20 1600 UTC (GMT)
- - -----------------------------------------------------------------------
Contents
========
Summary
Affected Products
Details
Impact
Software Version and Fixes
Workarounds
Obtaining Fixed Software
Exploitation and Public Announcements
Status of this Notice: FINAL
Distribution
Revision History
Cisco Security Procedures
- - -----------------------------------------------------------------------
Summary
=======
A vulnerability exists in certain Cisco IOS software release trains
running on the Cisco IAD2400 series, 1900 Series Mobile Wireless Edge
Routers and Cisco VG224 Analog Phone Gateways. Vulnerable versions may
contain a default hard-coded Simple Network Management Protocol (SNMP)
community string when SNMP is enabled on the device. The default
community string is a result of inadvertently identifying these devices
as supporting Data Over Cable Service Interface Specification (DOCSIS)
compliant interfaces. The consequence of this error is that an
additional read-write community string may be enabled if the device is
configured for SNMP management, allowing a knowledgeable attacker the
potential to gain privileged access to the device.
Cisco is making free software available to address this vulnerability
for affected customers. There are workarounds available to mitigate the
effects of the vulnerability.
This advisory is posted at
http://www.cisco.com/warp/public/707/cisco-sa-20060920-docsis.shtml.
Affected Products
=================
The following products are affected if they run a vulnerable release of
Cisco IOS software with the SNMP server enabled. Any version of Cisco
IOS software prior to the versions listed in the Fixed Software section
below may be vulnerable.
To determine if the SNMP server is running on your device and the
default community string is present, issue the "show snmp community"
command while in enable mode at the prompt and look for output similar
to:
Router#show snmp community
Community name: cable-docsis
Community Index: cisco0
Community SecurityName: cable-docsis
storage-type: read-only active
If the SNMP server is disabled on your device, output similar to the
following will be returned:
Router#show snmp community
%SNMP agent not enabled
To determine the software running on a Cisco product, log in to the
device and issue the "show version" command to display the system banner.
Cisco IOS software will identify itself as "Internetwork Operating
System Software" or simply "IOS". On the next line of output, the image
name will be displayed between parentheses, followed by "Version" and
the IOS release name. Other Cisco devices will not have the "show version"
command or will give different output.
The following example identifies a Cisco product running IOS release
12.2(15)MC2 with an installed image name of MWR1900-I-M:
Cisco Internetwork Operating System Software
IOS (tm) 1900 Software (MWR1900-I-M), Version 12.2(15)MC2, EARLY DEPLOYMENT RELEASE SOFTWARE (fc1)
Additional information about Cisco IOS release naming can be found at
http://www.cisco.com/warp/public/620/1.html.
Vulnerable Products
+------------------
Cisco devices that may be running with affected Cisco IOS software
releases include:
* Cisco IAD2430 Integrated Access Device
* Cisco IAD2431 Integrated Access Device
* Cisco IAD2432 Integrated Access Device
* Cisco VG224 Analog Phone Gateway
* Cisco MWR 1900 Mobile Wireless Edge Router
* Cisco MWR 1941 Mobile Wireless Edge Router
Products Confirmed Not Vulnerable
+--------------------------------
* Cisco IAD2420 Integrated Access Device
* Cisco IAD2421 Integrated Access Device
* Cisco IAD2423 Integrated Access Device
* Cisco IAD2424 Integrated Access Device
No other Cisco products are currently known to be affected by this
vulnerability.
Details
=======
Implementation of the Data Over Cable Service Interface Specification
(DOCSIS) standards allow for data transmission over physical media used
by cable television providers. Accordingly, RFC 2669
defines the DOCSIS Cable Device MIB, better known as the
DOCS-CABLE-DEVICE-MIB, for which support is required in order to be
considered DOCSIS compliant. That MIB defines the table,
docsDevNmAccessTable, as:
"This table controls access to SNMP objects by network
management stations. If the table is empty, access
to SNMP objects is unrestricted. This table exists only
on SNMPv1 or v2c agents and does not exist on SNMPv3
agents. See the conformance section for details.
Specifically, for v3 agents, the appropriate MIBs and
security models apply in lieu of this table."
In order to comply with the DOCSIS standard and to avoid unrestricted
access to SNMP objects, Cisco devices which support DOCSIS contain a
read-write community string, "cable-docsis".
Inclusion of this SNMP community string is intended only for
DOCSIS-compliant cable-capable devices. A vulnerability exists in the
inadvertent enabling of this community string in Cisco IOS release
trains running on the affected platforms.
Customers running vulnerable versions of Cisco IOS software on those
platforms may be unaware of the additional read-write community string.
This vulnerability is documented in Cisco Bug ID CSCsb04965
on the Cisco IAD2400 series and Cisco VG224 Analog Phone Gateways and
as CSCsb06658 on the 1900 Series Mobile Wireless Edge Routers.
Impact
======
Successful exploitation of the vulnerability may result in full control
of the device.
Software Version and Fixes
==========================
When considering software upgrades, also consult
http://www.cisco.com/go/psirt and any subsequent advisories to
determine exposure and a complete upgrade solution.
In all cases, customers should exercise caution to be certain the
devices to be upgraded contain sufficient memory and that current
hardware and software configurations will continue to be supported
properly by the new release. If the information is not clear, contact
the Cisco Technical Assistance Center ("TAC") or your contracted
maintenance provider for assistance.
Each row of the Cisco IOS software table (below) describes a release
train and the platforms or products for which it is intended. If a
given release train is vulnerable, then the earliest possible releases
that contain the fix (the "First Fixed Release") and the anticipated
date of availability for each are listed in the "Rebuild" and
"Maintenance" columns. A device running a release in the given train
that is earlier than the release in a specific column (less than the
First Fixed Release) is known to be vulnerable. The release should be
upgraded at least to the indicated release or a later version (greater
than or equal to the First Fixed Release label).
For more information on the terms "Rebuild" and "Maintenance," consult
the following URL: http://www.cisco.com/warp/public/620/1.html.
+-----------------------------------------------------------------------------+
| Major Release | Availability of Repaired Releases |
|------------------------------+----------------------------------------------|
| Affected 12.2-Based Release | Rebuild | Maintenance |
|------------------------------+---------------------+------------------------|
| 12.2MC | 12.2(15)MC2c | |
|------------------------------+----------------------------------------------|
| 12.2ZJ | Vulnerable; migrate to 12.3(4)T13 or later |
|------------------------------+----------------------------------------------|
| Affected 12.3-Based Release | Rebuild | Maintenance |
|------------------------------+---------------------+------------------------|
| | 12.3(4)T13 | |
| |---------------------+------------------------|
| | 12.3(7)T11 | |
| |---------------------+------------------------|
| 12.3T | 12.3(8)T10 | |
| |---------------------+------------------------|
| | 12.3(11)T6 | |
| |----------------------------------------------|
| | Vulnerable; for 12.3(14), migrate to |
| | 12.4(1b) or later |
|------------------------------+----------------------------------------------|
| 12.3XD | Vulnerable; migrate to 12.3(7)T11 or later |
|------------------------------+----------------------------------------------|
| 12.3XX | Vulnerable; migrate to 12.4(1b) or later |
|------------------------------+----------------------------------------------|
| 12.3XY | Vulnerable; migrate to 12.4(1b) or later |
|------------------------------+----------------------------------------------|
| 12.3YA | Vulnerable; contact TAC |
|------------------------------+----------------------------------------------|
| 12.3YD | Vulnerable; migrate to 12.4(2)T5 or later |
|------------------------------+----------------------------------------------|
| 12.3YF | Vulnerable; migrate to 12.3(14)YX or later |
|------------------------------+----------------------------------------------|
| 12.3YG | 12.3(14)YG5 | |
|------------------------------+----------------------------------------------|
| 12.3YH | Vulnerable; migrate to 12.4(2)T5 or later |
|------------------------------+----------------------------------------------|
| 12.3YI | Vulnerable; migrate to 12.4(2)T5 or later |
|------------------------------+----------------------------------------------|
| 12.3YJ | Vulnerable; migrate to 12.3(14)YQ8 or later |
|------------------------------+----------------------------------------------|
| 12.3YK | Vulnerable; migrate to 12.4(4)T or later |
|------------------------------+----------------------------------------------|
| 12.3YM | 12.3(14)YM8 | |
|------------------------------+---------------------+------------------------|
| 12.3YQ | 12.3(14)YQ8 | |
|------------------------------+----------------------------------------------|
| 12.3YS | Vulnerable; migrate to 12.4(4)T or later |
|------------------------------+----------------------------------------------|
| 12.3YT | Vulnerable; migrate to 12.4(4)T or later |
|------------------------------+----------------------------------------------|
| 12.3YU | Vulnerable; migrate to 12.4(2)XB or later |
|------------------------------+----------------------------------------------|
| Affected 12.4-Based Release | Rebuild | Maintenance |
|------------------------------+---------------------+------------------------|
| 12.4 | 12.4(1b) | 12.4(3) |
|------------------------------+---------------------+------------------------|
| 12.4MR | | 12.4(4)MR |
|------------------------------+---------------------+------------------------|
| 12.4T | 12.4(2)T5 | 12.4(4)T |
+-----------------------------------------------------------------------------+
Workarounds
===========
The effectiveness of any workarounds is dependent on specific customer
situations such as product mix, network topology, traffic behavior and
organizational mission. Due to the variety of affected products and
releases, customers should consult with their service provider or
support organization to ensure any applied workaround is the most
appropriate for use in the intended network before it is deployed.
The following workarounds should only be considered as a long term
solution if anti-spoofing methods consistently prevent spoofed source
attacks from entering the network and access-lists provided below are
configured on every potentially affected device.
Disable the SNMP Server
+----------------------
If the SNMP server is not used for any legitimate purposes on the
device, it is a best practice to disable it by issuing the following
commands in configure mode:
no snmp-server
Removing the public community string with the configure command
"no snmp-server community ro" is not sufficient as the SNMP server
will still be running and the device will be vulnerable. The command
"no snmp-server" must be used instead. The SNMP server status may be
verified by using the enable command "show snmp". You should see a
response of "%SNMP agent not enabled".
Note that this workaround may only be viable if SNMP is not used in any
way for managing the device.
Restrict Access via a Community-map
+----------------------------------
The ability to create a community-map was introduced in Cisco IOS
versions 12.0(23)S, 12.2(25)S and 12.3(2)T. This feature adds the
ability to create a mapping between an SNMP community and an SNMP
context, Engine ID, or security name that is different from the default
settings.
When an SNMP community is associated with an SNMP context, whenever a
request is made from this community, it is applied to the context
specified. This feature can also be used to specify the source address
validation for an SNMP community.
Consider the following example:
Router(config)#access-list 65 remark Deny access to community string
Router(config)#access-list 65 deny any
Router(config)#snmp-server community no-access RO 65
Router(config)#snmp mib community-map cable-docsis security-name no-access
The above creates a new community named "no-access". The authorization
to use the community "no-access" is controlled by an access-list, which
in this case denies all hosts from using it. With the addition of the
"snmp mib community-map" command, the current community string of
"cable-docsis" is then under the access restrictions of the new
community string "no-access" preventing any use of the "cable-docsis"
community string.
Control Plane Policing
+---------------------
Cisco IOS release trains 12.0S, 12.2SX, 12.2S, 12.3T, 12.4, and 12.4T
support Control Plane Policing (CoPP) which may be configured to
protect the device from attacks that target the management and control
planes. The following example can be adapted to your network. This
example assumes that all SNMP access is to be restricted to a
management station with the IP address of 10.1.1.1, and that the
management station need only communicate with router's IP address
192.168.10.1:
access-list 111 deny udp host 10.1.1.1 host 192.168.10.1 eq snmp
access-list 111 permit udp any any eq snmp
access-list 111 deny ip any any
!
class-map match-all drop-snmp-class
match access-group 111
!
!
policy-map drop-snmp-policy
class drop-snmp-class
drop
!
control-plane
service-policy input drop-snmp-policy
Please note that in the 12.0S, 12.2S, and 12.2SX Cisco IOS trains the
policy-map syntax is different:
policy-map drop-snmp-policy
class drop-snmp-class
police 32000 1500 1500 conform-action drop exceed-action drop
In the above CoPP examples the ACL entries that match the exploit
packets with the "permit" action result in these packets being
discarded by the policy-map "drop" function, while packets that match
the "deny" action are not affected by the policy-map drop function.
Additional information on the configuration and use of the CoPP feature
can be found at the following URL:
http://www.cisco.com/en/US/products/sw/iosswrel/ps1838/products_feature_guide09186a008052446b.html
Restrict Access to Trusted Hosts Only
+------------------------------------
Access Control Lists (ACLs) can be used to deny traffic to the device.
Although Cisco IOS devices have community-string access lists which
check the source address of SNMP requests per community string, they
will not work in this case as the cable-docsis community string is not
able to be modified or deleted via configuration options.
It is possible to permit UDP traffic to the router from trusted IP
addresses with interface ACLs.
Note: Because SNMP is based on UDP, it is possible to spoof the
sender's IP address, which may defeat ACLs that permit communication to
these ports from trusted IP addresses.
The following extended access-list can be adapted to your network. This
example assumes that the router has IP addresses 192.168.10.1 and
172.16.1.1 configured on its interfaces, that all SNMP access is to be
restricted to a management station with the IP address of 10.1.1.1, and
that the management station need only communicate with IP address
192.168.10.1:
access-list 101 permit udp host 10.1.1.1 host 192.168.10.1 eq snmp
access-list 101 deny udp any host 192.168.10.1 eq snmp
access-list 101 deny udp any host 172.16.1.1 eq snmp
access-list 101 permit ip any any
The access-list must then be applied to all interfaces using the
following configuration commands:
interface FastEthernet 0/0
ip access-group 101 in
Note that UDP traffic to port 161 (SNMP) must be explicitly blocked to
each IP address on the router to prevent the router from accepting and
processing the SNMP packets. Blocking traffic to port 161 from unknown
hosts is considered a best practice. All devices that need to
communicate directly with the router on port 161 will need to be
specifically listed in the above access list.
For devices that have many IP addresses configured, or many hosts that
need to communicate with the router, this may not be a scalable
solution.
Infrastructure ACLs (iACL)
+-------------------------
Although it is often difficult to block traffic transiting your
network, it is possible to identify traffic which should never be
allowed to target your infrastructure devices and block that traffic at
the border of your network. Infrastructure ACLs are considered a
network security best practice and should be considered as a long-term
addition to good network security as well as a workaround for this
specific vulnerability. The white paper entitled "Protecting Your Core:
Infrastructure Protection Access Control Lists" presents guidelines and
recommended deployment techniques for iACLs:
http://www.cisco.com/warp/public/707/iacl.html
Obtaining Fixed Software
========================
Cisco will make free software available to address this vulnerability
for affected customers. This advisory will be updated as fixed software
becomes available. Prior to deploying software, customers should
consult their maintenance provider or check the software for feature
set compatibility and known issues specific to their environment.
Customers may only install and expect support for the feature sets they
have purchased. By installing, downloading, accessing or otherwise
using such software upgrades, customers agree to be bound by the terms
of Cisco's software license terms found at
http://www.cisco.com/public/sw-license-agreement.html, or as otherwise
set forth at Cisco.com Downloads at
http://www.cisco.com/public/sw-center/sw-usingswc.shtml.
Do not contact either "psirt@cisco.com" or "security-alert@cisco.com"
for software upgrades.
Customers with Service Contracts
+-------------------------------
Customers with contracts should obtain upgraded software through their
regular update channels. For most customers, this means that upgrades
should be obtained through the Software Center on Cisco's worldwide
website at http://www.cisco.com.
Customers using Third Party Support Organizations
+------------------------------------------------
Customers whose Cisco products are provided or maintained through prior
or existing agreement with third-party support organizations such as
Cisco Partners, authorized resellers, or service providers should
contact that support organization for guidance and assistance with the
appropriate course of action in regards to this advisory.
The effectiveness of any workaround or fix is dependent on specific
customer situations such as product mix, network topology, traffic
behavior, and organizational mission. Due to the variety of affected
products and releases, customers should consult with their service
provider or support organization to ensure any applied workaround or
fix is the most appropriate for use in the intended network before it
is deployed.
Customers without Service Contracts
+----------------------------------
Customers who purchase direct from Cisco but who do not hold a Cisco
service contract and customers who purchase through third-party vendors
but are unsuccessful at obtaining fixed software through their point of
sale should get their upgrades by contacting the Cisco Technical
Assistance Center (TAC). TAC contacts are as follows.
* +1 800 553 2447 (toll free from within North America)
* +1 408 526 7209 (toll call from anywhere in the world)
* e-mail: tac@cisco.com
Have your product serial number available and give the URL of this
notice as evidence of your entitlement to a free upgrade. Free upgrades
for non-contract customers must be requested through the TAC.
Refer to http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml
for additional TAC contact information, including special localized
telephone numbers and instructions and e-mail addresses for use in
various languages.
Exploitation and Public Announcements
=====================================
The Cisco PSIRT is not aware of any public announcements or malicious
use of the vulnerability described in this advisory.
This vulnerability was reported to Cisco by a customer.
Status of this Notice: FINAL
============================
THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY
KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE
INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT
YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS
DOCUMENT AT ANY TIME.
A stand-alone copy or Paraphrase of the text of this document that
omits the distribution URL in the following section is an uncontrolled
copy, and may lack important information or contain factual errors.
Distribution
============
This advisory is posted on Cisco's worldwide website at:
http://www.cisco.com/warp/public/707/cisco-sa-20060920-docsis.shtml
In addition to worldwide web posting, a text version of this notice is
clear-signed with the Cisco PSIRT PGP key and is posted to the
following e-mail and Usenet news recipients.
* cust-security-announce@cisco.com
* first-teams@first.org
* bugtraq@securityfocus.com
* vulnwatch@vulnwatch.org
* cisco@spot.colorado.edu
* cisco-nsp@puck.nether.net
* full-disclosure@lists.grok.org.uk
* comp.dcom.sys.cisco@newsgate.cisco.com
Future updates of this advisory, if any, will be placed on Cisco's
worldwide website, but may or may not be actively announced on mailing
lists or newsgroups. Users concerned about this problem are encouraged
to check the above URL for any updates.
Revision History
================
+-----------------------------------------+
| Revision | | Initial |
| 1.0 | 2006-September-20 | public |
| | | release. |
+-----------------------------------------+
Cisco Security Procedures
=========================
Complete information on reporting security vulnerabilities in Cisco
products, obtaining assistance with security incidents, and registering
to receive security information from Cisco, is available on Cisco's
worldwide website at
http://www.cisco.com/en/US/products/products_security_vulnerability_policy.html.
This includes instructions for press inquiries regarding Cisco security
notices. All Cisco security advisories are available at
http://www.cisco.com/go/psirt.
- - -----------------------------------------------------------------------
All contents are Copyright 1992-2006 Cisco Systems, Inc. All rights
reserved.
- - -----------------------------------------------------------------------
Updated: Sep 20, 2006 Document ID: 71255
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2.
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Cisco Security Advisory: Cisco Intrusion Prevention System Management
Interface Denial of Service and Fragmented Packet Evasion Vulnerabilities
Document ID: 71558
Advisory ID: cisco-sa-20060920-ips
http://www.cisco.com/warp/public/707/cisco-sa-20060920-ips.shtml
Revision 1.0
For Public Release 2006 September 20 1600 UTC (GMT)
- - -----------------------------------------------------------------------
Contents
========
Summary
Affected Products
Details
Impact
Software Version and Fixes
Workarounds
Obtaining Fixed Software
Exploitation and Public Announcements
Status of this Notice: FINAL
Distribution
Revision History
Cisco Security Procedures
- - -----------------------------------------------------------------------
Summary
=======
Cisco Intrusion Prevention System (IPS) software contains a denial of
service vulnerability in web administration interface involving
malformed Secure Socket Layer (SSL) packets and a fragmented packet
evasion vulnerability.
There is a workaround for the web administration interface SSL denial
of service vulnerability. There is no workaround for the fragmented
packet IPS evasion vulnerability.
Cisco has made free software available to address these vulnerabilities
for affected customers.
This advisory is posted at
http://www.cisco.com/warp/public/707/cisco-sa-20060920-ips.shtml.
Affected Products
=================
Vulnerable Products
+------------------
The following Cisco IPS/IDS versions are vulnerable to the web
administration interface SSL denial of service issue:
* Cisco IDS 4.1(x) software prior to 4.1(5c)
* Cisco IPS 5.0(x) software prior to 5.0(6p1)
* Cisco IPS 5.1(x) software prior to 5.1(2)
The following Cisco IPS versions are vulnerable to the fragmented
packet IPS evasion issue:
* Cisco IPS 5.0(x) software prior to 5.0(6p2)
* Cisco IPS 5.1(x) software prior to 5.1(2)
All platforms running vulnerable versions of Cisco IPS/IDS software are
affected. This includes 4200 series appliances, IDSM2, NM-CIDS router
modules, and ASA IPS modules (also referred to as Advanced Inspection
and Prevention (AIP) Security Services Module [SSM]).
To determine the version of software running on an IPS/IDS device, log
in to the IPS/IDS device via SSH or the console and issue the command
show version.
sensor#show version
Application Partition: Cisco Intrusion
Prevention System, Version 5.1(2)S242.0
Products Confirmed Not Vulnerable
+--------------------------------
No other Cisco products are currently known to be affected by these
vulnerabilities.
Cisco IOS software images including the IPS feature set are not
vulnerable to the IPS evasion vulnerability if Virtual Fragment
Reassembly (VFR) is enabled. If VFR is not enabled, fragmented IP
traffic is not inspected by the IPS component which may allow malicious
traffic to evade detection. Please consult the IOS IPS documentation
for more information.
http://www.cisco.com/en/US/products/ps6634/products_white_paper0900aecd8043bc32.shtml
Details
=======
Cisco Intrusion Prevention and Detection Systems are a family of
network security devices that provide network-based threat prevention
services.
The web administration interface of Cisco IPS/IDS devices contains a
denial of service vulnerability. It is possible to send a malformed
SSLv2 Client Hello packet to the IPS/IDS web administration interface,
which may cause the process (mainApp) responsible for managing remote
access to fail. This results in an IPS/IDS device becoming unresponsive
to all future remote management requests through the web administration
interface or the command-line interface (CLI) via SSH and the console.
This vulnerability is documented in Cisco bug IDs CSCsd91720 and
CSCsd92033. This vulnerability was originally fixed in Cisco IPS
version 5.1(2).
By using a specially crafted sequence of fragmented IP packets, it is
possible for malicious traffic to evade inspection by a Cisco IPS
device. This may allow an attacker to circumvent the protection
provided by an IPS device and access internal systems. IPS devices
running in inline and promiscuous modes are affected. This
vulnerability is documented in Cisco bug IDs CSCse17206 and CSCsf12379.
This vulnerability was originally fixed in Cisco IPS version 5.1(2).
Impact
======
Successful exploitation of the web administration interface SSL denial
of service vulnerability may result in the failure of the mainApp
process. If the mainApp process fails, the following tasks will cease
operation:
* Reporting alerts to remote monitoring systems
* Automated modification of access control lists (ACLs) on remote
firewall systems (PIX and IOS)
* Sending SNMP traps
Even though the mainApp has failed, the IPS/IDS device will continue to
perform inspection of traffic for malicious activity. If configured,
the device will continue to drop packets/connections inline and send
TCP resets in response to any malicious activity. IPS/IDS devices must
be rebooted to recover from this vulnerability. If an IPS/IDS device is
configured with a service account, it is possible to log in to an
affected device with the service account via SSH or the console and
manually reboot the device.
Successful exploitation of the fragmented packet IPS evasion
vulnerability may result in an attacker being able to evade detection
by an IPS device. This could allow protected systems to be covertly
attacked.
Software Version and Fixes
==========================
When considering software upgrades, also consult
http://www.cisco.com/go/psirt and any subsequent advisories to
determine exposure and a complete upgrade solution.
In all cases, customers should exercise caution to be certain the
devices to be upgraded contain sufficient memory and that current
hardware and software configurations will continue to be supported
properly by the new release. If the information is not clear, contact
the Cisco Technical Assistance Center ("TAC") or your contracted
maintenance provider for assistance.
+--------------------------------------------+
| Affected Software | Fixed Software |
| Version | Version |
|----------------------+---------------------|
| Cisco IDS 4.1(5b) | Cisco IDS 4.1(5c) |
| and earlier | |
|----------------------+---------------------|
| Cisco IPS 5.0(6p1) | Cisco IPS 5.0(6p2) |
| and earlier | |
|----------------------+---------------------|
| Cisco IPS 5.1(1) and | Cisco IPS 5.1(2) |
| earlier | |
+--------------------------------------------+
Note: IPS version 5.1(2) is no longer available for download. It has
been replaced by IPS version 5.1(3).
Note: Bug ID CSCsd91720 is fixed in IPS version 5.0(6p1), and CSCsf12379
is fixed in IPS version 5.0(6p2).
Fixed software for Cisco IPS versions 5.1(x) are available for download
at http://www.cisco.com/pcgi-bin/tablebuild.pl/ips5?psrtdcat20e2
Fixed software for Cisco IPS versions 4.1(x) and 5.0(x) is available
for download at
http://www.cisco.com/pcgi-bin/tablebuild.pl/ids-patches?psrtdcat20e2
Workarounds
===========
It is possible to limit exposure to the web administration interface
SSL denial of service vulnerability by applying an access control list
(ACL) on an IPS/IDS device to restrict access to trusted management
systems. Instructions to add an ACL can be found at:
http://www.cisco.com/en/US/products/hw/vpndevc/ps4077/products_configuration_guide_chapter09186a008055df9a.html#wp1031536
There is no workaround for the fragmented packet IPS evasion
vulnerability.
Obtaining Fixed Software
========================
Cisco will make free software available to address this vulnerability
for affected customers. This advisory will be updated as fixed software
becomes available. Prior to deploying software, customers should
consult their maintenance provider or check the software for feature
set compatibility and known issues specific to their environment.
Customers may only install and expect support for the feature sets they
have purchased. By installing, downloading, accessing or otherwise
using such software upgrades, customers agree to be bound by the terms
of Cisco's software license terms found at
http://www.cisco.com/public/sw-license-agreement.html, or as otherwise
set forth at Cisco.com Downloads at
http://www.cisco.com/public/sw-center/sw-usingswc.shtml.
Do not contact either "psirt@cisco.com" or "security-alert@cisco.com"
for software upgrades.
Customers with Service Contracts
+-------------------------------
Customers with contracts should obtain upgraded software through their
regular update channels. For most customers, this means that upgrades
should be obtained through the Software Center on Cisco's worldwide
website at http://www.cisco.com.
Customers using Third Party Support Organizations
+------------------------------------------------
Customers whose Cisco products are provided or maintained through prior
or existing agreement with third-party support organizations such as
Cisco Partners, authorized resellers, or service providers should
contact that support organization for guidance and assistance with the
appropriate course of action in regards to this advisory.
The effectiveness of any workaround or fix is dependent on specific
customer situations such as product mix, network topology, traffic
behavior, and organizational mission. Due to the variety of affected
products and releases, customers should consult with their service
provider or support organization to ensure any applied workaround or
fix is the most appropriate for use in the intended network before it
is deployed.
Customers without Service Contracts
+----------------------------------
Customers who purchase direct from Cisco but who do not hold a Cisco
service contract and customers who purchase through third-party vendors
but are unsuccessful at obtaining fixed software through their point of
sale should get their upgrades by contacting the Cisco Technical
Assistance Center (TAC). TAC contacts are as follows.
* +1 800 553 2447 (toll free from within North America)
* +1 408 526 7209 (toll call from anywhere in the world)
* e-mail: tac@cisco.com
Have your product serial number available and give the URL of this
notice as evidence of your entitlement to a free upgrade. Free upgrades
for non-contract customers must be requested through the TAC.
Refer to http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml
for additional TAC contact information, including special localized
telephone numbers and instructions and e-mail addresses for use in
various languages.
Exploitation and Public Announcements
=====================================
The Cisco PSIRT is not aware of any public announcements or malicious
use of the vulnerability described in this advisory.
The web administration interface SSL denial of service vulnerability
was discovered internally by Cisco.
The fragmented packet IPS evasion vulnerability was reported to Cisco
by Pratap Ramamurthy and Shai Rubin of the Wisconsin Safety Analyzer
group (WiSA) in the Computer Science department at the University of
Wisconsin.
Status of this Notice: FINAL
============================
THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY
KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE
INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT
YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS
DOCUMENT AT ANY TIME.
A stand-alone copy or Paraphrase of the text of this document that
omits the distribution URL in the following section is an uncontrolled
copy, and may lack important information or contain factual errors.
Distribution
============
This advisory is posted on Cisco's worldwide website at:
http://www.cisco.com/warp/public/707/cisco-sa-20060920-ips.shtml
In addition to worldwide web posting, a text version of this notice is
clear-signed with the Cisco PSIRT PGP key and is posted to the
following e-mail and Usenet news recipients.
* cust-security-announce@cisco.com
* first-teams@first.org
* bugtraq@securityfocus.com
* vulnwatch@vulnwatch.org
* cisco@spot.colorado.edu
* cisco-nsp@puck.nether.net
* full-disclosure@lists.grok.org.uk
* comp.dcom.sys.cisco@newsgate.cisco.com
Future updates of this advisory, if any, will be placed on Cisco's
worldwide website, but may or may not be actively announced on mailing
lists or newsgroups. Users concerned about this problem are encouraged
to check the above URL for any updates.
Revision History
================
+----------------------------------------+
| Revision | | Initial |
| 1.0 | 2006-August-20 | public |
| | | release. |
+----------------------------------------+
Cisco Security Procedures
=========================
Complete information on reporting security vulnerabilities in Cisco
products, obtaining assistance with security incidents, and registering
to receive security information from Cisco, is available on Cisco's
worldwide website at
http://www.cisco.com/en/US/products/products_security_vulnerability_policy.html.
This includes instructions for press inquiries regarding Cisco security
notices. All Cisco security advisories are available at
http://www.cisco.com/go/psirt.
- - -----------------------------------------------------------------------
All contents are Copyright 1992-2006 Cisco Systems, Inc. All rights
reserved.
- - -----------------------------------------------------------------------
Updated: Sep 20, 2006 Document ID: 71558
- - -----------------------------------------------------------------------
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3.
- -----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
Cisco Security Advisory: Cisco Guard Enables Cross Site Scripting
Advisory ID: cisco-sa-20060920-guardxss
http://www.cisco.com/warp/public/707/cisco-sa-20060920-guardxss.shtml
Revision 1.0
For Public Release 2006 September 20 1600 UTC (GMT)
+--------------------------------------------------------------------
Contents
========
Summary
Affected Products
Details
Impact
Software Version and Fixes
Workarounds
Obtaining Fixed Software
Exploitation and Public Announcements
Status of this Notice: FINAL
Distribution
Revision History
Cisco Security Procedures
+---------------------------------------------------------------------
Summary
=======
A vulnerability in the Cisco Guard may enable an attacker to send a
web browser client to a malicious website with the use of Cross Site
Scripting (XSS) when the Guard is providing anti-spoofing services
between the web browser client and a webserver. The attacker may
exploit this by providing a malicious URL for the web browser client
to go to, often in email, followed off of a malicious website, or in
an instant message. This issue may occur even if the protected
website does not allow XSS. A software upgrade is required to fix
this vulnerability. There is a workaround available to mitigate the
effects of the vulnerability.
This advisory is available at
http://www.cisco.com/warp/public/707/cisco-sa-20060920-guardxss.shtml.
Affected Products
=================
The Cisco Guard is the only affected product. Details are available
below.
Vulnerable Products
+------------------
The following Cisco products are vulnerable.
* Cisco Guard Appliance (Software Version 3.X)
* Cisco Guard Blade (Software Version 4.X)
* Cisco Guard Appliance [Software Version 5.0(3)]
* Cisco Guard Appliance [Software Version 5.1(5)]
Products Confirmed Not Vulnerable
+--------------------------------
No other Cisco products have been found to be vulnerable.
There are three ways to determine the software version that your
Cisco Guard DDoS mitigation appliance is running. An example of each
method is shown here:
* Virtual terminal or local serial console connection
To determine the software version number through the local serial
console use a serial cable and a terminal emulation program to
connect to the appliance. Once you are connected, press the Enter
key of your terminal and the Guard will present, without even
logging in, the version of the software running on the devices:
Cisco Guard Version 3.1(0.12)
GUARD login:
In this example the Cisco Guard is running software version 3.1.
For a virtual terminal, the procedure is the same except that no
serial cable or terminal emulation program is needed (a standard
keyboard and monitor are directly connected to the appliance).
* Remote Secure Shell (SSH) connection
To obtain the software version number through a SSH session, use
a SSH client to log in to the Cisco Guard and issue the show
version command-line interface (CLI) command.
prompt$ ssh admin@guard.example.com
admin@guard.example.com's password:
Last login: Wed Nov 24 22:45:53 on ttyS0
admin@GUARD#show version
Copyright (c) 2000-2004 Cisco Systems, Inc. All rights reserved.
Software License Agreement
[...]
Cisco Anomaly Guard
Release: 3.1(0.12)
Date: 2004/10/27 19:58:14
GUARD uptime is 3 weeks, 3 days, 17 hours, 53 minutes
System Serial Number: XXXXXXX
In this example, the Cisco Traffic Anomaly Guard is running
software version 3.1.
* Remote secure web session
To obtain the software version that Cisco Guard is running
through a secure web interface, open the URL
https://IP address of your Guard/ in a web browser, log in,
and then click on the About link located on the top right section
of the browser window.
Details
=======
The Cisco Guard DDoS Mitigation Appliance is a distributed
denial-of-service (DDoS) protection system. Malicious DOS traffic is
identified with a Cisco Detector and diverted to the Guard for attack
mitigation. Under normal circumstances, the Guard plays no role in
valid traffic; it is specifically designed to deal with large volumes
of invalid traffic.
Cross Site Scripting (XSS) is an attack where a user follows a link
that contains an embedded script. The link often looks valid, and
sends the user to a valid site. The recipient website does not
contain the link that is sent and sends a meta-refresh back to the
user without validating the data it is sent. When receiving the
meta-refresh, the web browser interprets the script as an instruction
from the website and the script is executed on the user's machine .
In this case, when the anti-spoofing feature is enabled, all diverted
HTTP traffic is inspected and then a meta-refresh is sent to the
client containing the original request. If the original URL contains
a script and a specific character sequence, the meta-refresh from the
Guard will allow the client machine to execute the malicious script.
Several conditions are required to be true in order for the malicious
script to be processed:
* The client user must follow a URL with a specifically formatted,
embedded script to a site protected by the Guard.
* The Guard must be running active basic protection, going through
basic/redirect protection.
* The specially crafted http request must be diverted through the
Guard, and processed by the Guard.
Only if all of the above conditions are met will the client receive
the meta-refresh and process the embedded script.
This vulnerability is being tracked by bug ID CSCsf01438.
Impact
======
Successful exploitation of the vulnerability may result in malicious
executable code being run by an individual user using a web browser.
Software Version and Fixes
==========================
When considering software upgrades, also consult
http://www.cisco.com/go/psirt and any subsequent advisories to
determine exposure and a complete upgrade solution.
This vulnerability is fixed in version 5.1(6) of the Cisco Anomaly
Guard code.
In all cases, customers should exercise caution to be certain the
devices to be upgraded contain sufficient memory and that current
hardware and software configurations will continue to be supported
properly by the new release. If the information is not clear, contact
the Cisco Technical Assistance Center ("TAC") or your contracted
maintenance provider for assistance.
Workarounds
===========
Changing the basic/redirect protection to basic/safe-reset protects
the client from executing the embedded script. Instead of providing a
layer seven http meta-refresh to the browser with the malicious URL
intact, the Guard provides a layer three TCP-RST to end the
connection. This can cause minor compatability issues, as some
firewalls do not forward the TCP-RST. However, this method protects
users from any XSS attacks until the Guard can be upgraded to a fixed
version of code.
To turn off basic/redirect and configure basic/safe-reset, please
follow the example below.
1. Show the zone.
user@GUARD#show zone test
...skipped
**** USER FILTERS ****
Row Source IP Source Mask Proto DPort Frg Action Rate Burst Units RxRate(pps)
10 * 255.255.255.255 6 80 no basic/redirect
user@GUARD#config t
user@GUARD-conf#zone test
user@GUARD-conf-zone-test# no user-filter 10
2. Configure basic/safe-reset dynamic filter.
user@GUARD-conf-zone-test#user-filter 10 basic/safe-reset * 6 80
3. Show that the filter is applied.
user@GUARD#show zone test
...skipped
**** USER FILTERS ****
Row Source IP Source Mask Proto DPort Frg Action Rate Burst Units RxRate(pps)
10 * 255.255.255.255 6 80 no basic/safe-reset
For more information, please refer to the configuration guide:
http://www.cisco.com/en/US/products/ps5888/products_configuration_guide_chapter09186a00804b7d13.html#wp1135548
Obtaining Fixed Software
========================
Cisco will make free software available to address this vulnerability
for affected customers. This advisory will be updated as fixed
software becomes available. Prior to deploying software, customers
should consult their maintenance provider or check the software for
feature set compatibility and known issues specific to their
environment.
Customers may only install and expect support for the feature sets
they have purchased. By installing, downloading, accessing or
otherwise using such software upgrades, customers agree to be bound by
the terms of Cisco's software license terms found at
http://www.cisco.com/public/sw-license-agreement.html, or as otherwise
set forth at Cisco.com Downloads at
http://www.cisco.com/public/sw-center/sw-usingswc.shtml.
Do not contact either "psirt@cisco.com" or "security-alert@cisco.com"
for software upgrades.
Customers with Service Contracts
+-------------------------------
Customers with contracts should obtain upgraded software through their
regular update channels. For most customers, this means that upgrades
should be obtained through the Software Center on Cisco's worldwide
website at
http://www.cisco.com/cgi-bin/tablebuild.pl/cisco-ga-crypto
for the appliance or
http://www.cisco.com/cgi-bin/tablebuild.pl/cisco-agm-crypto
for the 7600 module.
Customers using Third Party Support Organizations
+------------------------------------------------
Customers whose Cisco products are provided or maintained through
prior or existing agreement with third-party support organizations
such as Cisco Partners, authorized resellers, or service providers
should contact that support organization for guidance and assistance
with the appropriate course of action in regards to this advisory.
The effectiveness of any workaround or fix is dependent on specific
customer situations such as product mix, network topology, traffic
behavior, and organizational mission. Due to the variety of affected
products and releases, customers should consult with their service
provider or support organization to ensure any applied workaround or
fix is the most appropriate for use in the intended network before it
is deployed.
Customers without Service Contracts
+----------------------------------
Customers who purchase direct from Cisco but who do not hold a Cisco
service contract and customers who purchase through third-party
vendors but are unsuccessful at obtaining fixed software through
their point of sale should get their upgrades by contacting the Cisco
Technical Assistance Center (TAC). TAC contacts are as follows.
* +1 800 553 2447 (toll free from within North America)
* +1 408 526 7209 (toll call from anywhere in the world)
* e-mail: tac@cisco.com
Have your product serial number available and give the URL of this
notice as evidence of your entitlement to a free upgrade. Free
upgrades for non-contract customers must be requested through the
TAC.
Refer to http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml
for additional TAC contact information, including special localized
telephone numbers and instructions and e-mail addresses for use in
various languages.
Exploitation and Public Announcements
=====================================
The Cisco PSIRT is not aware of any public announcements or malicious
use of the vulnerability described in this advisory.
This vulnerability was reported to Cisco by a customer.
Status of this Notice: FINAL
============================
THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY
KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE
INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS
AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS
DOCUMENT AT ANY TIME.
A stand-alone copy or Paraphrase of the text of this document that
omits the distribution URL in the following section is an
uncontrolled copy, and may lack important information or contain
factual errors.
Distribution
============
This advisory is posted on Cisco's worldwide website at:
http://www.cisco.com/warp/public/707/cisco-sa-20060920-guardxss.shtml
In addition to worldwide web posting, a text version of this notice
is clear-signed with the Cisco PSIRT PGP key and is posted to the
following e-mail and Usenet news recipients.
* cust-security-announce@cisco.com
* first-teams@first.org
* bugtraq@securityfocus.com
* vulnwatch@vulnwatch.org
* cisco@spot.colorado.edu
* cisco-nsp@puck.nether.net
* full-disclosure@lists.grok.org.uk
* comp.dcom.sys.cisco@newsgate.cisco.com
Future updates of this advisory, if any, will be placed on Cisco's
worldwide website, but may or may not be actively announced on
mailing lists or newsgroups. Users concerned about this problem are
encouraged to check the above URL for any updates.
Revision History
================
+-----------------------------------------+
| Revision | | Initial |
| 1.0 | 2006-September-20 | public |
| | | release. |
+-----------------------------------------+
Cisco Security Procedures
=========================
Complete information on reporting security vulnerabilities in Cisco
products, obtaining assistance with security incidents, and
registering to receive security information from Cisco, is available
on Cisco's worldwide website at
http://www.cisco.com/en/US/products/products_security_vulnerability_policy.html
This includes instructions for press inquiries regarding Cisco
security notices. All Cisco security advisories are available at
http://www.cisco.com/go/psirt.
- - ---------------------------------------------------------------------
All contents are Copyright (C) 1992-2006 Cisco Systems, Inc. All rights
reserved.
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