January 2005
Cisco Security Advisory: Vulnerability in Cisco IOS Embedded Call Processing Solutions
ID: 00047
Ref: 43/2005
Date: 20 January 2005:11:35:49
Version: 1
Title: Cisco Security Advisory: Vulnerability in Cisco IOS Embedded Call Processing Solutions
Abstract:
Vendors affected: Cisco
Operating systems affected: Cisco
Applications affected: Cisco
Title
=====
Cisco Security Advisory: Vulnerability in Cisco IOS Embedded Call
Processing Solutions
Detail
======
Cisco Internetwork Operating System (IOS®) Software release trains 12.1YD,
12.2T, 12.3 and 12.3T, when configured for the Cisco IOS Telephony Service
(ITS), Cisco CallManager Express (CME) or Survivable Remote Site Telephony
(SRST) may contain a vulnerability in processing certain malformed control
protocol messages
- -----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
Cisco Security Advisory: Vulnerability in Cisco IOS Embedded Call
Processing Solutions
Revision 1.0
For Public Release 2005 January 19 1500 UTC
+----------------------------------------------------------------------
Contents
========
Summary
Affected Products
Details
Impact
Software Versions and Fixes
Obtaining Fixed Software
Workarounds
Exploitation and Public Announcements
Status of This Notice: FINAL
Distribution
Revision History
Cisco Security Procedures
+----------------------------------------------------------------------
Summary
=======
Cisco Internetwork Operating System (IOS®) Software release trains 12.1YD,
12.2T, 12.3 and 12.3T, when configured for the Cisco IOS Telephony Service
(ITS), Cisco CallManager Express (CME) or Survivable Remote Site Telephony
(SRST) may contain a vulnerability in processing certain malformed control
protocol messages.
A successful exploitation of this vulnerability may cause a reload of the
device and could be exploited repeatedly to produce a Denial of Service
(DoS). This advisory is available at
http://www.cisco.com/warp/public/707/cisco-sa-20050119-itscme.shtml
Cisco has made free software upgrades available to address this vulnerability
for all affected customers. There are workarounds available to mitigate
the effects of the vulnerability.
This vulnerability is documented by Cisco bug ID CSCee08584.
Affected Products
=================
Vulnerable Products
+------------------
This issue affects all Cisco devices running any unfixed version of
Cisco IOS code that supports, and is configured for ITS, CME or SRST.
A Cisco device running ITS or CME will have the following line in the
configuration:
telephony-service
A Cisco device running SRST will have the following line in the
configuration:
call-manager-fallback
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
12.0(3) with an installed image name of C2500-IS-L:
Cisco Internetwork Operating System Software IOS (TM)
2500 Software (C2500-IS-L), Version 12.0(3), RELEASE SOFTWARE
The release train label is "12.0".
The next example shows a product running IOS release 12.3(6) with an image
name of C2600-JS-MZ:
Cisco Internetwork Operating System Software IOS (tm)
C2600 Software (C2600-JS-MZ), Version 12.3(6), RELEASE SOFTWARE (fc1)
Additional information about Cisco IOS release naming can be found at
http://www.cisco.com/warp/public/620/1.html.
Products Confirmed Not Vulnerable
+--------------------------------
ITS, CME and SRST are IOS-only features. Devices that do not run IOS are
not vulnerable.
Details
========
More information about Cisco's IOS Telephony Service (ITS) and Cisco
CallManager Express (CME) can be found here:
http://www.cisco.com/en/US/products/sw/voicesw/ps4625/index.html
More information on Cisco's Survivable Remote Site Telephony (SRST) can
be found here:
http://www.cisco.com/en/US/products/sw/voicesw/ps2169/index.html
ITS, CME and SRST are features that allow a Cisco device running IOS to
control IP Phones using the Skinny Call Control Protocol (SCCP). SCCP
is the Cisco CallManager native signaling protocol.
Certain malformed packets sent to the SCCP port on an IOS device
configured for ITS, CME or SRST may cause the target device to reload.
This issue is documented in Cisco bug ID CSCee08584.
The following commands can be used to determine if ITS or CME are running.
A device that does not have ITS or CME enabled will display:
Router#show telephony-service
telephony-service is not enabled
A device that has ITS or CME enabled will show something similar to:
Router#show telephony-service
CONFIG (Version=3.0)
=====================
Cisco CallManager Express
ip source-address 192.168.1.1 port 2000
max-ephones 2
max-dn 2
max-conferences 8
max-redirect 5
time-format 12
date-format mm-dd-yy
keepalive 30
timeout interdigit 10
timeout busy 10
timeout ringing 180
edit DN through Web: disabled.
edit TIME through web: disabled.
Log (table parameters):
max-size: 150
retain-timer: 15
create cnf-files version-stamp Jan 01 2002 00:00:00
auto assign 1 to 2
local directory service: enabled.
The following commands can be used to determine if SRST is running.
A device that does not have SRST enabled will display:
Router#show call-manager-fallback
Call-manager fallback is not enabled
A device that has SRST enabled will show something similar to:
Router#show call-manager-fallback
CONFIG
======
ip source-address 192.168.1.1 port 2000
max-ephones 2
max-dn 4
huntstop
time-format 12
date-format mm-dd-yy
keepalive 30
interdigit timeout 10
busy timeout 10
Limit number of DNs per phone:
7910: 34
7935: 34
7940: 34
7960: 34
Spoofed attacks are impractical since the attacker must pass all of
the TCP/IP integrity checks first, including the initial sequence
number and source TCP port number.
Impact
======
Successful exploitation of the vulnerability may result in a device
reload. Repeated exploitation could result in a Denial of Service
(DoS) attack.
Software Versions and Fixes
===========================
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 further information on the terms "Rebuild" and "Maintenance"
please consult the following URL:
http://www.cisco.com/warp/public/620/1.html
When considering software upgrades, please also consult
http://www.cisco.com/en/US/products/products_security_advisories_listing.html
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") for asssistance.
+------------------------------------------+
| Major | Availability of Repaired |
| Release | Releases |
|------------+-----------------------------|
| Affected | | |
| 12.1-Based | Rebuild | Maintenance |
| Release | | |
|------------+-----------------------------|
| 12.1YD | Migrate to 12.2(15)T13 |
| | or later |
|------------+-----------------------------|
| 12.1YE | Migrate to 12.2(15)T13 |
| | or later |
|------------+-----------------------------|
| 12.1YI | Migrate to 12.2(15)T13 |
| | or later |
|------------+-----------------------------|
| Affected | | |
| 12.2-Based | Rebuild | Maintenance |
| Release | | |
|------------+-----------------------------|
| 12.2B | Migrate to 12.3(8)T or |
| | later |
|------------+-----------------------------|
| 12.2BC | Migrate to 12.3(9)BC or |
| | later |
|------------+-----------------------------|
| 12.2CZ | Migrate to 12.2(15)CZ1 |
| | or later |
|------------+-----------------------------|
| 12.2JK | 12.2(15)JK2 |
|------------+-----------------------------|
| | 12.2(13) | |
| | T14 | |
|12.2T |------------+----------------|
| | 12.2(15) | |
| | T13 | |
|------------+-----------------------------|
| 12.2XB | Migrate to 12.3(9) or |
| | later |
|------------+-----------------------------|
| 12.2XG | Migrate to 12.2(15)T13 |
| | or later |
|------------+-----------------------------|
| 12.2XM | Migrate to 12.2(15)T13 |
| | or later |
|------------+-----------------------------|
| 12.2XT | Migrate to 12.2(15)T13 |
| | or later |
|------------+-----------------------------|
| 12.2XU | Migrate to 12.2(15)T13 |
| | or later |
|------------+-----------------------------|
| 12.2XW | Migrate to 12.2(15)T13 |
| | or later |
|------------+-----------------------------|
| 12.2XZ | Migrate to 12.2(15)T13 |
| | or later |
|------------+-----------------------------|
| 12.2YA | 12.2(4)YA8 | |
|------------+-----------------------------|
| 12.2YB | Migrate to 12.2(15)T13 |
| | or later |
|------------+-----------------------------|
| 12.2YC | Migrate to 12.2(15)T13 |
| | or later |
|------------+-----------------------------|
| 12.2YD | Migrate to 12.3(8)T or |
| | later |
|------------+-----------------------------|
| 12.2YF | Migrate to 12.2(15)T13 |
| | or later |
|------------+-----------------------------|
| 12.2YG | Migrate to 12.2(15)T13 |
| | or later |
|------------+-----------------------------|
| 12.2YH | Migrate to 12.2(15)T13 |
| | or later |
|------------+-----------------------------|
| 12.2YJ | Migrate to 12.2(15)T13 |
| | or later |
|------------+-----------------------------|
| 12.2YL | Migrate to 12.3(8)T or |
| | later |
|------------+-----------------------------|
| 12.2YM | Migrate to 12.3(8)T or |
| | later |
|------------+-----------------------------|
| 12.2YN | Migrate to 12.3(8)T or |
| | later |
|------------+-----------------------------|
| 12.2YQ | Migrate to 12.3(8)T or |
| | later |
|------------+-----------------------------|
| 12.2YR | Migrate to 12.3(8)T or |
| | later |
|------------+-----------------------------|
| 12.2YS | Migrate to 12.3(8)T or |
| | later |
|------------+-----------------------------|
| 12.2ZK | Migrate to 12.3(8)T or |
| | later |
|------------+-----------------------------|
| 12.2ZO | Migrate to 12.2(15)T13 |
| | or later |
|------------+-----------------------------|
| 12.2ZP | Migrate to 12.3(4)XN2 or |
| | later |
|------------+-----------------------------|
| Affected | | |
| 12.3-Based | Rebuild | Maintenance |
| Release | | |
|------------+------------+----------------|
| | 12.3(5d) | |
| |------------+----------------|
| 12.3 | 12.3(6c) | |
| |------------+----------------|
| | | 12.3(9) |
|------------+------------+----------------|
| | 12.3(2)T7 | |
| |------------+----------------|
| | 12.3(4)T6 | |
|12.3T |------------+----------------|
| | 12.3(7)T1 | |
| |------------+----------------|
| | | 12.3(8)T |
|------------+-----------------------------|
| 12.3XA | Migrate to 12.3(8)T or |
| | later |
|------------+-----------------------------|
| 12.3XB | Migrate to 12.3(8)T or |
| | later |
|------------+-----------------------------|
| 12.3XC | Migrate to 12.3(8)T or |
| | later |
|------------+-----------------------------|
| 12.3XD | 12.3(4)XD3 | |
|------------+------------+----------------|
| 12.3XE | 12.3(2)XE1 | |
|------------+-----------------------------|
| 12.3XF | Migrate to 12.3(11)T or |
| | later |
|------------+-----------------------------|
| 12.3XG | 12.3(4)XG2 | |
|------------+-----------------------------|
| 12.3XH | Migrate to 12.3(11)T or |
| | later |
|------------+-----------------------------|
| 12.3XI | | 12.3(7)XI |
|------------+------------+----------------|
| 12.3XJ | 12.3(7)XJ2 | |
|------------+------------+----------------|
| 12.3XK | 12.3(4)XK1 | |
|------------+------------+----------------|
| 12.3XL | | 12.3(7)XL |
|------------+-----------------------------|
| 12.3XN | Contact Cisco TAC |
|------------+-----------------------------|
| | 12.3(4)XQ1 | |
| | Release | |
| 12.3XQ | date not | |
| | yet | |
| | determined | |
+------------------------------------------+
Obtaining Fixed Software
========================
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 assistance with the
upgrade, which should be free of charge.
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 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
Please 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.
Please do not contact either "psirt@cisco.com" or
"security-alert@cisco.com" for software upgrades.
See 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.
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.
Workarounds
===========
The effectiveness of any workaround 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.
Affected devices that must run ITS, CME or SRST are vulnerable, and
there are not any specific configurations that can be used to protect
them. Applying access lists on interfaces that should not accept ITS,
CME or SRST traffic and putting firewalls in strategic locations may
greatly reduce exposure until an upgrade can be performed.
The IP Telephony Security in Depth SAFE paper at the URL below discusses
a variety of best practices that should keep your voice network isolated
from the Internet. These best practices may help to reduce the risk of
exposure, although attacks from within the local network should always
be considered a potential risk.
http://www.cisco.com/en/US/netsol/ns340/ns394/ns171/ns128/networking_solutions_white_paper09186a00801b7a50.shtml
Using 'strict-match'
+-------------------
It is possible to restrict SCCP communications to the IP specified
in the ip source-address configuration command by using the strict-match
option. More information on this command can be found at the following
URL:
http://www.cisco.com/en/US/netsol/ns340/ns394/ns165/ns391/networking_solutions_design_guidance09186a00801f8e30.html#wp40333
Using Access Lists
+-----------------
Where possible, it is recommended to block SCCP traffic at the network
edge with an Infrastructure Access Control List (iACL) or a Transit
Access Control List (tACL).
For more information on iACLs, refer to "Protecting Your Core:
Infrastructure Protecton Access Control Lists":
http://www.cisco.com/warp/public/707/iacl.html
For more information on tACLs, refer to 'Transit Access Control
Lists: Filtering at Your Edge":
http://www.cisco.com/warp/public/707/tacl.html
Below is an example of an access list to block SCCP traffic from
anywhere but a permitted network.
Note: In SRST deployments the SCCP packets are not addressed directly
to the SRST device. The SCCP packets will be addressed to the call
control devices (typically Cisco CallManager).
In this example, the permitted telephony devices are on the 172.16.0.0/16
network and the SCCP port being used is the default, TCP port 2000.
If the specific IP addresses of the telephony devices are known, then
the access list can be made to restrict traffic from only those devices.
!--- Permit access from any IP address in the 172.16.0.0/16
!--- to TCP port 2000.
access-list 101 permit tcp 172.16.0.0 0.0.255.255 any eq 2000
!--- Deny all traffic to port 2000.
access-list 101 deny tcp any any eq 2000
!--- Permit all other traffic.
access-list 101 permit ip any any
Using Control Plane Policing
+---------------------------
The Control Plane Policing (CoPP) feature may be used to mitigate this
vulnerability. In the following example SCCP traffic is permitted to
and from the 192.168.10.0/24 subnet. All other TCP port 2000 traffic
destined to the device is blocked.
access-list 140 deny tcp 192.168.10.0 0.0.0.255 any eq 2000
access-list 140 deny tcp any 192.168.10.0 0.0.0.255 eq 2000
access-list 140 permit tcp any any eq 2000
access-list 140 deny ip any any
class-map match-all sccp-class
match access-group 140
policy-map control-plane-policy
class sccp-class
police 8000 1500 1500 conform-action drop exceed-action drop
control-plane
service-policy input control-plane-policy
CoPP is available in IOS release trains 12.2S and 12.3T. 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_guide09186a00801afad4.html
Exploitation and Public Announcements =====================================
The vulnerability described by CSCee08584 was originally reported to
Cisco by SecureTest. The Cisco PSIRT is not aware of any public
announcements or malicious use of the vulnerability described in
this advisory.
Status of This Notice: FINAL
============================
THIS ADVISORY IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY
KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTY OF MERCHANTABILITY.
YOUR USE OF THE INFORMATION ON THE ADVISORY OR MATERIALS LINKED FROM THE
ADVISORY IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE
THIS NOTICE AT ANY TIME.
A stand-alone copy or paraphrase of the text of this security advisory
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 will be posted on Cisco's worldwide website at
http://www.cisco.com/warp/public/707/cisco-sa-20050119-itscme.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 (includes CERT/CC)
* bugtraq@securityfocus.com
* vulnwatch@vulnwatch.org
* cisco@spot.colorado.edu
* cisco-voice@puck.nether.net
* full-disclosure@lists.netsys.com
* 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 | 2005-Jan-19 | 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
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