Cisco Security Advisory: Cisco IOS Software Border Gateway Protocol 4-Byte Autonomous System Number Vulnerabilities

2009-07-29T00:00:00
ID SECURITYVULNS:DOC:22239
Type securityvulns
Reporter Securityvulns
Modified 2009-07-29T00:00:00

Description

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1

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
Copyright (c) 1986-2008 by cisco Systems, Inc.   
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 Copyright (c) 1986-2008 by Cisco Systems, Inc. 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

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