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July 2009

3872 - Cisco Security Advisory: IOS Border Gateway Vulnerability

ID: 3872
Date: 30/07/2009

Title: 3872 - Cisco Security Advisory: IOS Border Gateway Vulnerability
Platform level affected:Hardware
Hardware components affected:Network Router/Switch/Modem
Specific operating systems components affected: Cisco IOS
Net-enabled software: Other
Security software:Other
Other software: Other
Remediation Summary:Other
Vendors affected:Cisco
Applications affected:IOS versions 12.0S, 12.0SY, 12.2SXI, 12.2XND, 12.4T
Adversity source: Unknown
Attack Vector: DoS
Virulence: Unknown
Warning Status: Unknown
Potential Damage: Network DOS
Possible Duration: Unknown
Availability of fix: Available
Type of fix: Workaround
Source: Cisco
Reliability of source: Trusted
Source URL: http://www.cisco.com/warp/public/707/cisco-sa-20090729-bgp.shtml
Abstract: Advisory concerning vulnerabilities on Cisco devices running IOS Software with support for four-octet AS number space.

* PGP Signed: 07/29/09 at 15:57:32

Cisco Security Advisory: Cisco IOS Software Border Gateway Protocol

4-Byte Autonomous System Number

Vulnerabilities

Advisory ID: cisco-sa-20090729-bgp

http://www.cisco.com/warp/public/707/cisco-sa-20090729-bgp.shtml

Revision: 1.0

=========

For Public Release 2009 July 29 1600 UTC (GMT)

Summary

=======

Recent versions of Cisco IOS Software support RFC4893 ("BGP Support

for Four-octet AS Number Space") and contain two remote denial of

service (DoS) vulnerabilities when handling specific Border Gateway

Protocol (BGP) updates.

These vulnerabilities affect only devices running Cisco IOS Software

with support for four-octet AS number space (here after referred to as

4-byte AS number) and BGP routing configured.

The first vulnerability could cause an affected device to reload when

processing a BGP update that contains autonomous system (AS) path

segments made up of more than one thousand autonomous systems.

The second vulnerability could cause an affected device to reload when

the affected device processes a malformed BGP update that has been

crafted to trigger the issue.

Cisco has released free software updates to address these

vulnerabilities.

No workarounds are available for the first vulnerability.

A workaround is available for the second vulnerability.

This advisory is posted at the following link:

http://www.cisco.com/warp/public/707/cisco-sa-20090729-bgp.shtml

Affected Products

=================

Vulnerable Products

+------------------

These vulnerabilities affect only devices running Cisco IOS and

Cisco IOS XE Software (here after both referred to as simply Cisco

IOS) with support for RFC4893 and that have been configured for

BGP routing.

The software table in the section "Software Versions and Fixes" of

this advisory indicates all affected Cisco IOS Software versions that

have support for RFC4893 and are affected by this vulnerability.

A Cisco IOS software version that has support for RFC4893 will allow

configuration of AS numbers using 4 Bytes. The following example

identifies a Cisco device that has 4 byte AS number support:

Router#configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

Router(config)#router bgp ?

<1-65535> Autonomous system number

<1.0-XX.YY> 4 Octets Autonomous system number

Or:

Router#configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

Router(config)#router bgp ?

<1-4294967295> Autonomous system number

<1.0-XX.YY> Autonomous system number

The following example identifies a Cisco device that has 2 byte AS

number support:

Router#configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

Router(config)#router bgp ?

<1-65535> Autonomous system number

A router that is running the BGP process will contain a line in the

configuration that defines the autonomous system number (AS number),

which can be seen by issuing the command line interface (CLI) command

"show running-config".

The canonical textual representation of four byte AS Numbers is

standardized by the IETF through RFC5396 (Textual Representation of

Autonomous System (AS) Numbers). Two major ways for textual

representation have been defined as ASDOT and ASPLAIN. Cisco IOS

routers support both textual representations of AS numbers. For

further information about textual representation of four byte AS

numbers in Cisco IOS Software consult the document "Explaining 4-Byte

Autonomous System (AS) ASPLAIN and ASDOT Notation for Cisco IOS" at

the following link:

http://www.cisco.com/en/US/prod/collateral/iosswrel/ps6537/ps6554/ps6599/white_paper_c11_516829.html

Cisco IOS Software with support for RFC4893 is affected by both

vulnerabilities if BGP routing is configured using either ASPLAIN or

ASDOT notation.

The following example identifies a Cisco device that is configured

for BGP using ASPLAIN notation:

router bgp 65536

The following example identifies a Cisco device that is configured

for BGP using ASDOT notation:

router bgp 1.0

To determine the Cisco IOS Software release that is running on a

Cisco product, administrators can log in to the device and issue the

show version command to display the system banner. The system banner

confirms that the device is running Cisco IOS Software by displaying

text similar to "Cisco Internetwork Operating System Software" or

"Cisco IOS Software." The image name displays in parentheses,

followed by "Version" and the Cisco IOS Software release name. Other

Cisco devices do not have the show version command or may provide

different output.

The following example identifies a Cisco product that is running

Cisco IOS Software Release 12.3(26) with an installed image name of

C2500-IS-L:

Router#show version

Cisco Internetwork Operating System Software

IOS (tm) 2500 Software (C2500-IS-L), Version 12.3(26), RELEASE SOFTWARE (fc2)

Technical Support: http://www.cisco.com/techsupport

Compiled Mon 17-Mar-08 14:39 by dchih

!--- output truncated

The following example identifies a Cisco product that is running

Cisco IOS Software Release 12.4(20)T with an installed image name of

C1841-ADVENTERPRISEK9-M:

Router#show version

Cisco IOS Software, 1841 Software (C1841-ADVENTERPRISEK9-M), Version 12.4(20)T, RELEASE SOFTWARE (fc3)

Technical Support: http://www.cisco.com/techsupport

Compiled Thu 10-Jul-08 20:25 by prod_rel_team

!--- output truncated

Additional information about Cisco IOS Software release naming

conventions is available in "White Paper: Cisco IOS Reference Guide"

at the following link: http://www.cisco.com/warp/public/620/1.html

Products Confirmed Not Vulnerable

+--------------------------------

The following Cisco products are confirmed not vulnerable:

* Cisco IOS Software not explicitly mentioned in this Advisory

* Cisco IOS XR Software

* Cisco IOS NX-OS

No other Cisco products are currently known to be affected by this

vulnerability.

Details

=======

RFC4271 has defined an AS number as a two-octet entity in BGP.

RFC4893 has defined an AS number as a four-octet entity in BGP.

The first vulnerability could cause an affected device to reload when

processing a BGP update that contains AS path segments made up of more

than one thousand autonomous systems. If an affected 4-byte AS number

BGP speaker receives a BGP update from a 2-byte AS number BGP speaker

that contains AS path segments made up of more than one thousand

autonomous systems, the device may crash with memory corruption, and

the error "%%Software-forced reload" will be displayed.

The following three conditions are required for successful

exploitation of this vulnerability:

* Affected Cisco IOS Software device is a 4-byte AS number BGP

speaker

* BGP peering neighbor is a 2-byte AS number BGP speaker

* BGP peering neighbor is capable of sending a BGP update with a

series of greater than one thousand AS numbers

Note: Note: Cisco IOS, Cisco IOS XE, Cisco NX-OS and Cisco IOS XR

Software, as a 2 byte AS number BGP speaker send BGP updates with

a maximum of 255 AS numbers.

This vulnerability is documented in Cisco Bug ID CSCsy86021 and has

been assigned Common Vulnerabilities and Exposures (CVE) ID

CVE-2009-1168.

The second vulnerability could cause an affected device to reload when

the affected device processes a malformed BGP update that has been

crafted to trigger the issue. The following three conditions are

required for successful exploitation of this vulnerability:

* Affected Cisco IOS Software device is a 4-byte AS number BGP

speaker

* BGP peering neighbor is a 2-byte AS number BGP speaker

* BGP peering neighbor is capable of sending a non-RFC compliant

crafted BGP update message

This vulnerability is documented in Cisco Bug ID CSCta33973 and has

been assigned Common Vulnerabilities and Exposures (CVE) ID

CVE-2009-2049.

Further information regarding Cisco support for 4-byte AS number is

available in "Cisco IOS BGP 4-Byte ASN Support" at the following

link:

http://www.cisco.com/en/US/prod/collateral/iosswrel/ps6537/ps6554/ps6599/data_sheet_C78-521821.html

Vulnerability Scoring Details

=============================

Cisco has provided scores for the vulnerabilities in this advisory

based on the Common Vulnerability Scoring System (CVSS). The CVSS

scoring in this Security Advisory is done in accordance with CVSS

version 2.0.

CVSS is a standards-based scoring method that conveys vulnerability

severity and helps determine urgency and priority of response.

Cisco has provided a base and temporal score. Customers can then

compute environmental scores to assist in determining the impact of

the vulnerability in individual networks.

Cisco has provided an FAQ to answer additional questions regarding

CVSS at

http://www.cisco.com/web/about/security/intelligence/cvss-qandas.html

Cisco has also provided a CVSS calculator to help compute the

environmental impact for individual networks at

http://intellishield.cisco.com/security/alertmanager/cvss

CSCsy86021: Cisco IOS Software BGP Long AS-path Vulnerability

CVSS Base Score - 7.1

Access Vector Network

Access Complexity Medium

Authentication None

Confidentiality Impact None

Availability Impact Complete

CVSS Temporal Score - 6.7

Exploitability Functional

Remediation Level Official-Fix

Report Confidence Confirmed

CSCta33973: Cisco IOS Software Crafted BGP Update Message Vulnerability

CVSS Base Score - 5.4

Access Vector Network

Access Complexity High

Authentication None

Confidentiality Impact None

Availability Impact Complete

CVSS Temporal Score - 4.5

Exploitability Functional

Remediation Level Official-Fix

Report Confidence Confirmed

Impact

======

Successful exploitation of the vulnerabilities described in this

document may result in a reload of the device. The issue could result

in repeated exploitation to cause an extended DoS condition.

Software Versions 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) names a Cisco IOS

release train. If a given release train is vulnerable, then the

earliest possible releases that contain the fix (along with the

anticipated date of availability for each, if applicable) are listed

in the "First Fixed Release" column of the table. The "Recommended

Release" column indicates the releases which have fixes for all the

published vulnerabilities at the time of this Advisory. 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. Cisco recommends upgrading to a release equal to or

later than the release in the "Recommended Releases" column of the

table.

+-------------------------------------------------------------------+

| Major | Availability of Repaired Releases |

| Release | |

|----------+--------------------------------------------------------|

| Affected | |Recommended |

|12.0-Based| First Fixed Release | Release |

| Releases | | |

|----------+-------------------------------------------+------------|

|12.0 |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0DA |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0DB |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0DC |Not Vulnerable | |

|----------+-------------------------------------------+------------|

| |Releases up to and including 12.0(32)S11 | |

| |are not vulnerable; first fixed in | |

|12.0S |12.0(32)S14; | |

| | | |

| |Releases up to and including 12.0(33)S2 are| |

| |not vulnerable; first fixed in 12.0(33)S5 | |

|----------+-------------------------------------------+------------|

|12.0SC |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0SL |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0SP |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0ST |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0SX |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0SY |Releases up to and including 12.0(32)SY7 |12.0(32)SY10|

| |are not vulnerable; first fixed in | |

| |12.0(32)SY9a. | |

|----------+-------------------------------------------+------------|

|12.0SZ |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0T |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0W |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0WC |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0WT |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0WX |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0XA |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0XB |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0XC |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0XD |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0XE |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0XF |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0XG |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0XH |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0XI |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0XJ |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0XK |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0XL |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0XM |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0XN |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0XQ |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0XR |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0XS |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0XT |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0XV |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.0XW |Not Vulnerable | |

|----------+-------------------------------------------+------------|

| Affected | |Recommended |

|12.1-Based| First Fixed Release | Release |

| Releases | | |

|-------------------------------------------------------------------|

| There are no affected 12.1 based releases |

|-------------------------------------------------------------------|

| Affected | |Recommended |

|12.2-Based| First Fixed Release | Release |

| Releases | | |

|----------+-------------------------------------------+------------|

|12.2 |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2B |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2BC |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2BW |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2BX |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2BY |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2BZ |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2CX |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2CY |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2CZ |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2DA |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2DD |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2DX |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2EW |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2EWA |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2EX |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2EY |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2EZ |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2FX |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2FY |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2FZ |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2IRA |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2IRB |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2IRC |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2IXA |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2IXB |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2IXC |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2IXD |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2IXE |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2IXF |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2IXG |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2IXH |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2JA |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2JK |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2MB |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2MC |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2S |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SB |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SBC |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SCA |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SCB |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SE |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SEA |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SEB |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SEC |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SED |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SEE |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SEF |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SEG |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SG |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SGA |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SL |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SM |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SO |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SQ |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SRA |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SRB |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SRC |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SRD |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2STE |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SU |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SV |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SVA |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SVC |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SVD |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SVE |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SW |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SX |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SXA |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SXB |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SXD |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SXE |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SXF |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SXH |Not Vulnerable | |

|----------+-------------------------------------------+------------|

| |Releases up to and including 12.2(33)SXI | |

|12.2SXI |are not vulnerable; CSCsy86021 first fixed | |

| |in 12.2(33)SXI2; CSCta33973 first fixed in | |

| |12.2(33)SXI3 | |

|----------+-------------------------------------------+------------|

|12.2SY |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2SZ |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2T |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2TPC |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2XA |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2XB |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2XC |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2XD |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2XE |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2XF |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2XG |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2XH |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2XI |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2XJ |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2XK |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2XL |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2XM |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2XN |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2XNA |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2XNB |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2XNC |12.2(33)XNC2 | |

|----------+-------------------------------------------+------------|

|12.2XND |12.2(33)XND1; available 25th August 2009 | |

|----------+-------------------------------------------+------------|

|12.2XO |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2XQ |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2XR |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2XS |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2XT |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2XU |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2XV |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2XW |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2YA |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2YB |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2YC |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2YD |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2YE |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2YF |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2YG |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2YH |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2YJ |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2YK |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2YL |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2YM |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2YN |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2YO |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2YP |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2YQ |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2YR |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2YS |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2YT |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2YU |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2YV |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2YW |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2YX |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2YY |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2YZ |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2ZA |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2ZB |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2ZC |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2ZD |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2ZE |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2ZF |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2ZG |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2ZH |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2ZJ |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2ZL |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2ZM |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2ZP |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2ZU |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2ZX |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2ZY |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.2ZYA |Not Vulnerable | |

|----------+-------------------------------------------+------------|

| Affected | |Recommended |

|12.3-Based| First Fixed Release | Release |

| Releases | | |

|-------------------------------------------------------------------|

| There are no affected 12.3 based releases |

|-------------------------------------------------------------------|

| Affected | |Recommended |

|12.4-Based| First Fixed Release | Release |

| Releases | | |

|----------+-------------------------------------------+------------|

|12.4 |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4JA |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4JDA |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4JDC |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4JDD |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4JK |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4JL |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4JMA |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4JMB |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4JX |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4MD |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4MDA |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4MR |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4SW |Not Vulnerable | |

|----------+-------------------------------------------+------------|

| |Releases up to 12.4(24)T are not | |

|12.4T |vulnerable; first fixed in 12.4(24)T2 | |

| |available on 23-Oct-2009 | |

|----------+-------------------------------------------+------------|

|12.4XA |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4XB |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4XC |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4XD |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4XE |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4XF |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4XG |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4XJ |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4XK |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4XL |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4XM |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4XN |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4XP |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4XQ |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4XR |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4XT |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4XV |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4XW |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4XY |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4XZ |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4YA |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4YB |Not Vulnerable | |

|----------+-------------------------------------------+------------|

|12.4YD |Not Vulnerable | |

+-------------------------------------------------------------------+

Cisco IOS XE Release Table

+-------------------------

+-------------------------------------------------------------------+

| Major | Availability of Repaired Releases |

| Release | |

|----------+--------------------------------------------------------|

| Affected | |

| 2.1 | There are no affected 2.1 based releases |

| Releases | |

|----------+--------------------------------------------------------|

| Affected | |

| 2.2 | There are no affected 2.2 based releases |

| Releases | |

|----------+--------------------------------------------------------|

| Affected | Releases up to and including 2.3.1t are vulnerable; |

| 2.3 | First fixed in 2.3.2 |

| Releases | |

|----------+--------------------------------------------------------+

| Affected | Releases up to and including 2.4.0 are vulnerable; |

| 2.4 | First fixed in 2.4.1, available 25th August 2009 |

| Releases | |

+----------+--------------------------------------------------------+

Workarounds

===========

For the first vulnerability, there are no workarounds on the affected

device. Neighbors could be configured to discard routes that have

more than one thousand AS numbers in the AS-path segments. This

configuration will help prevent the further propagation of BGP

updates with the AS path segments made up of greater than one

thousand AS numbers.

Note: Configuring "bgp maxas-limit [value]" on the affected device

does not mitigate this vulnerability.

For the second vulnerability, configuring "bgp maxas-limit [value]"

on the affected device does mitigate this vulnerability. Cisco is

recommends using a conservative value of 100 to mitigate this

vulnerability.

Consult the document "Protecting Border Gateway Protocol for the

Enterprise" at the following link for additional best practices on

protecting BGP infrastructures:

http://www.cisco.com/web/about/security/intelligence/protecting_bgp.html

Obtaining Fixed Software

========================

Cisco has released free software updates that address these

vulnerabilities. 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/en/US/docs/general/warranty/English/EU1KEN_.html

or as otherwise set forth at Cisco.com Downloads at

http://www.cisco.com/public/sw-center/sw-usingswc.shtml

Do not contact 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 agreements 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 do not hold a Cisco

service contract, and customers who purchase through third-party

vendors but are unsuccessful in obtaining fixed software through

their point of sale should acquire 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

Customers should have their product serial number available and be

prepared to give the URL of this notice as evidence of entitlement to

a free upgrade. Free upgrades for non-contract customers must be

requested through the TAC.

Refer to

http://www.cisco.com/en/US/support/tsd_cisco_worldwide_contacts.html

for additional TAC contact information, including 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 malicious exploitation of either of

these vulnerabilities, although we are aware of some customers who

have seen the first vulnerability triggered within their

infrastructures. Further investigation of those incidents seems to

indicate that the vulnerability has been accidentally triggered.

These vulnerabilities were discovered via internal product testing.

Status of this Notice: FINAL

============================

This information is Cisco Highly Confidential - Do not redistribute.

THIS IS A DRAFT VERSION OF A SECURITY NOTICE THAT CONTAINS UNRELEASED

INFORMATION ABOUT CISCO PRODUCTS. DISTRIBUTION WITHIN CISCO IS

LIMITED TO PERSONNEL WITH A NEED TO KNOW. THIS DRAFT MAY CONTAIN

ERRORS OR OMIT IMPORTANT INFORMATION.

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.

Distribution

============

This advisory is posted on Cisco's worldwide website at:

http://www.cisco.com/warp/public/707/cisco-sa-20090729-bgp.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-bulletins@lists.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 1.0 | 2009-July-29 1600 | Initial 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

* Cisco Systems Product Security Incident Response Team <psirt@cisco.com>

* 0xCF14FEE0(L)

This advisory contains information released by the original author. Some of the information may have changed since it was released. If the issue affects you, it may be prudent to retrieve the advisory from the site of the original source to ensure that you receive the most current information concerning that problem. Reference to any specific commercial product, process, or service by trade name, trademark manufacturer, or otherwise, does not constitute or imply its endorsement, recommendation, or favouring by CPNI.

The views and opinions of authors expressed within this notice shall not be used for advertising or product endorsement purposes. CPNI shall not accept responsibility for any errors or omissions contained within this advisory. In particular, they shall not be liable for any loss or damage whatsoever, arising from or in connection with the usage of information contained within this advisory.

CSIRTUK is a member of the Forum of Incident Response and Security Teams (FIRST) and has contacts with other international Incident Response Teams (IRTs) in order to foster cooperation and coordination in incident prevention, to prompt rapid reaction to incidents, and to promote information sharing amongst its members and the community at large.