Products & Services
Support

Product Categories


Popular Downloads


Manage Software

How to Buy

For Home

Linksys Products Store
Linksys is now part of Belkin
Products for everyone

All Ordering Options

Training & Events Partners
Guest

Cisco Security Advisory

Cisco IOS Software Malformed Border Gateway Protocol Attribute Vulnerability

Advisory ID: cisco-sa-20120926-bgp

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120926-bgp

Revision 1.1

Last Updated  2012 October 4 15:33  UTC (GMT)

For Public Release 2012 September 26 16:00  UTC (GMT)


Summary

Cisco IOS Software contains a vulnerability in the Border Gateway Protocol (BGP) routing protocol feature. 

The vulnerability can be triggered when the router receives a malformed attribute from a peer on an existing BGP session.

Successful exploitation of this vulnerability can cause all BGP sessions to reset.  Repeated exploitation may result in an inability to route packets to BGP neighbors during reconvergence times.

Cisco has released free software updates that address this vulnerability.  There are no workarounds for this vulnerability.  This advisory is available at the following link:
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120926-bgp

Note: The September 26, 2012, Cisco IOS Software Security Advisory bundled publication includes nine Cisco Security Advisories. Eight of the advisories address vulnerabilities in Cisco IOS Software, and one advisory addresses a vulnerability in Cisco Unified Communications Manager. Each Cisco IOS Software Security Advisory lists the Cisco IOS Software releases that correct the vulnerability or vulnerabilities detailed in the advisory as well as the Cisco IOS Software releases that correct all Cisco IOS Software vulnerabilities in the September 2012 bundled publication. 

Individual publication links are in "Cisco Event Response: Semi-Annual Cisco IOS Software Security Advisory Bundled Publication" at the following link:

http://www.cisco.com/web/about/security/intelligence/Cisco_ERP_sep12.html

Affected Products

This vulnerability affects Cisco IOS Software, Cisco IOS-XR Software, and Cisco IOS-XE Software. 

Vulnerable Products

A Cisco IOS router is potentially vulnerable when it is running an affected version of Cisco IOS Software, BGP routing is enabled on the router, and the router has at least one established BGP neighbor session.  For more information on affected versions, see the "Software Versions and Fixes" section below.

A device running Cisco IOS XR has a vulnerable configuration if BOTH of the following conditions are true:

1.  BGP mVPN routing is enabled and a neighbor is configured.  The following example shows configuration commands that will be present:
router bgp <as-id>
address-family <ipv4 | ipv6> mvpn
neighbor <neighbor-ip>
2.  A neighbor session is established.

Note: For Cisco IOS XR, the only vulnerable configuration is address-family <ipv4|ipv6> mvpn as noted above. BGP mVPN with MDT is NOT affected.

A device running Cisco IOS has an affected configuration if BOTH of the following conditions are true:

1.  BGP routing is enabled and a neighbor is configured.  The following example shows configuration commands that will be present:
router bgp <as-id>
neighbor <neighbor-ip>
2.  A BGP neighbor session is established.


You can determine if a BGP session is established using the show ip bgp summary command in Cisco IOS Software.  In Cisco IOS XR software, you can determine if a BGP session is established using the show bgp <ipv4 | ipv6> mvpn all summary command.  The following example shows the output from an IOS router with two neighbor sessions established:

Router# show ip bgp summary 
!--- output shortened
Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down State/PfxRcd
10.100.1.1      4   200      26      22      199    0    0 00:14:23 23
10.200.1.1      4   300      21      51      199    0    0 00:13:40 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 15.0(1)M1 with an installed image name of C3900-UNIVERSALK9-M:

Router> show version 
Cisco IOS Software, C3900 Software (C3900-UNIVERSALK9-M), Version 15.0(1)M1, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2009 by Cisco Systems, Inc.
Compiled Wed 02-Dec-09 17:17 by prod_rel_team
!--- output truncated 

Additional information about Cisco IOS Software release naming conventions is available in "White Paper: Cisco IOS and NX-OS Software Reference Guide" at http://www.cisco.com/web/about/security/intelligence/ios-ref.html.

Products Confirmed Not Vulnerable

A Cisco IOS router is not vulnerable if BGP is not running, or if BGP does not have at least one neighbor session established.  No other Cisco products are currently known to be affected by this vulnerability.  Cisco NXOS Software is not affected.

The following example shows output from a router with BGP enabled, two neighbors configured, but with no sessions established with the remote BGP peers:

Router# show ip bgp summary 
!--- output shortened
Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down State/PfxRcd
10.100.1.1      4   200      0       0        0    0    0 never    Idle
10.200.1.1      4   300      0       2        0    0    0 never    Idle

Details

Cisco IOS Software contains a vulnerability in the BGP routing protocol feature.  This vulnerability affects Cisco IOS Software, Cisco IOS-XR Software, and Cisco IOS-XE Software.  Cisco NXOS Software is not affected.

The vulnerability may be triggered when the router receives a malformed attribute from a peer on an existing BGP session.  At least one BGP neighbor session must be established for a router to be vulnerable.

Successful exploitation of this vulnerability may cause all BGP peers to reset.  Repeated exploitation may result in an inability to route packets to BGP neighbors during reconvergence times.

This vulnerability is documented in Cisco bug IDs CSCtt35379 (registered customers only) and CSCty58300 (registered customers only) and has been assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2012-4617.  The corresponding Cisco IOS XR Software bug IDs are CSCtz63248 (registered customers only) and CSCtz62914 (registered customers only)

Vulnerability Scoring Details

Cisco has scored the vulnerability in this advisory based on the Common Vulnerability Scoring System (CVSS). The CVSS scoring in this security advisory is in accordance with CVSS version 2.0.

CVSS is a standards-based scoring method that conveys vulnerability severity and helps organizations determine the urgency and priority of a response.

Cisco has provided a base and temporal score. Customers can also compute environmental scores that help determine the impact of the vulnerability in their own networks.

Cisco has provided additional information regarding CVSS at the following link:

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

Cisco has also provided a CVSS calculator to compute the environmental impact for individual networks at the following link:

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



CSCtt35379 - BGP Processing Enhancements and CSCty58300 - BGP Processing Enhancements

Calculate the environmental score of CSCtt35379 and CSCty58300

CVSS Base Score - 7.1

Access Vector

Access Complexity

Authentication

Confidentiality Impact

Integrity Impact

Availability Impact

Network

Medium

None

None

None

Complete

CVSS Temporal Score - 5.9

Exploitability

Remediation Level

Report Confidence

Functional

Official-Fix

Confirmed




  CSCtz63248 - Improper checks for BGP attributes and CSCtz62914 - BGP handling of invalid attribute needs to be more robust

Calculate the environmental score of CSCtz63248 and CSCtz62914

CVSS Base Score - 7.1

Access Vector

Access Complexity

Authentication

Confidentiality Impact

Integrity Impact

Availability Impact

Network

Medium

None

None

None

Complete

CVSS Temporal Score - 5.9

Exploitability

Remediation Level

Report Confidence

Functional

Official-Fix

Confirmed


Impact

Successful exploitation of the vulnerability may cause all BGP peers to reset.  Repeated exploitation may result in an inability to route packets to BGP neighbors during reconvergence times.

Software Versions and Fixes

When considering software upgrades, customers are advised to consult the Cisco Security Advisories and Responses archive at http://www.cisco.com/go/psirt and review subsequent advisories to determine exposure and a complete upgrade solution.

In all cases, customers should ensure that the devices to be upgraded contain sufficient memory and confirm that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, customers are advised to contact the Cisco Technical Assistance Center (TAC) or their contracted maintenance providers.

Cisco IOS Software

Each row of the following Cisco IOS Software table corresponds to a Cisco IOS Software train. If a particular train is vulnerable, the earliest releases that contain the fix are listed in the First Fixed Release column. The First Fixed Release for All Advisories in the September 2012 Bundled Publication column lists the earliest possible releases that correct all the published vulnerabilities in the Cisco IOS Software Security Advisory bundled publication. Cisco recommends upgrading to the latest available release, where possible.

The Cisco IOS Software Checker allows customers to search for Cisco Security Advisories that address specific Cisco IOS Software releases. This tool is available on the Cisco Security Intelligence Operations (SIO) portal at http://tools.cisco.com/security/center/selectIOSVersion.x



Major Release      Availability of Repaired Releases
Affected 12.0-Based Releases First Fixed Release First Fixed Release for All Advisories in the September 2012 Cisco IOS Software Security Advisory Bundled Publication
There are no affected 12.0 based releases
Affected 12.2-Based Releases First Fixed Release First Fixed Release for All Advisories in the September 2012 Cisco IOS Software Security Advisory Bundled Publication
There are no affected 12.2 based releases
Affected 12.3-Based Releases First Fixed Release First Fixed Release for All Advisories in the September 2012 Cisco IOS Software Security Advisory Bundled Publication
There are no affected 12.3 based releases
Affected 12.4-Based Releases First Fixed Release First Fixed Release for All Advisories in the September 2012 Cisco IOS Software Security Advisory Bundled Publication
There are no affected 12.4 based releases
Affected 15.0-Based Releases First Fixed Release First Fixed Release for All Advisories in the September 2012 Cisco IOS Software Security Advisory Bundled Publication
There are no affected 15.0 based releases
Affected 15.1-Based Releases First Fixed Release First Fixed Release for All Advisories in the September 2012 Cisco IOS Software Security Advisory Bundled Publication
There are no affected 15.1 based releases
Affected 15.2-Based Releases First Fixed Release First Fixed Release for All Advisories in the September 2012 Cisco IOS Software Security Advisory Bundled Publication
15.2GC Not vulnerable
Releases prior to 15.2(3)GC are vulnerable; Releases 15.2(3)GC and later are not vulnerable. First fixed in Release 15.2T
15.2JA Not vulnerable
Not Vulnerable
15.2M Not vulnerable

Not vulnerable
15.2S 15.2(1)S0a
15.2(1)S2

Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
15.2(1)S2
15.2(2)S1
15.2(4)S

Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
15.2SNG Not vulnerable
Not vulnerable
15.2T Not vulnerable
15.2(1)T3
15.2(2)T2
15.2(3)T2; Available on 12-OCT-12

Cisco IOS XE Software

Cisco IOS XE is affected by the vulnerability described in this advisory.

Cisco IOS XE Software Release First Fixed Release First Fixed Release for All Advisories in the September 2012 Cisco IOS Software Security Advisory Bundled Publication
2.1.x Not vulnerable Vulnerable; migrate to 3.6.0S or later.
2.2.x Not vulnerable Vulnerable; migrate to 3.6.0S or later.
2.3.x Not vulnerable Vulnerable; migrate to 3.6.0S or later.
2.4.x Not vulnerable Vulnerable; migrate to 3.6.0S or later.
2.5.x Not vulnerable Vulnerable; migrate to 3.6.0S or later.
2.6.x Not vulnerable Vulnerable; migrate to 3.6.0S or later.
3.1.xS Not vulnerable 3.1.4S
3.1.xSG Not vulnerable Vulnerable; migrate to 3.2.5SG or later.
3.2.xS Not vulnerable Vulnerable; migrate to 3.6.0S or later.
3.2.xSG Not vulnerable 3.2.5SG
3.2.xSO Not vulnerable Vulnerable; migrate to 3.3.1SG or later.
3.3.xS Not vulnerable Vulnerable; migrate to 3.6.0S or later.
3.3xSG Not vulnerable 3.3.1SG
3.4.xS Not vulnerable Vulnerable; migrate to 3.6.0S or later.
3.5.xS 3.5.2S Vulnerable; migrate to 3.6.0S or later.
3.6.xS Not vulnerable Not vulnerable
3.7xS Not vulnerable Not vulnerable

Cisco IOS XR Software

Cisco IOS XR Software Releases 4.1.0, 4.1.1, 4.1.2, 4.2.0, 4.2.1, and 4.2.2 are affected by the vulnerability described in this advisory.


Release Platform CSCtz62914 SMU ID CSCtz63248 SMU ID
4.1.0 c12k AA06458 AA06464
4.1.0 CRS AA06437 AA06399
4.1.0 asr9k AA06449 AA06444
4.1.1 c12k AA06459 AA06465
4.1.1 CRS AA06438 AA06400
4.1.1 asr9k AA06450 AA06445
4.1.2 c12k AA06460 AA06466
4.1.2 CRS AA06439 AA06401
4.1.2 asr9k AA06451 AA06446
4.2.0 c12k AA06461 AA06467
4.2.0 CRS AA06440 AA06402
4.2.0 asr9k AA06452 AA06447
4.2.0 asr9k (PX) AA06453 AA06448
4.2.1 c12k AA06462 AA06546
4.2.1 CRS AA06441 AA06547
4.2.1 asr9k  AA06454 AA06548
4.2.1 asr9k (PX) AA06455 AA06549
4.2.2 asr9k AA06581 AA06550
4.2.2 asr9k (PX) AA06582 AA06551



Workarounds

There are no workarounds for this vulnerability.

A reference document that may be useful is the "Protecting BGP" white paper here: http://www.cisco.com/web/about/security/intelligence/protecting_bgp.html

Obtaining Fixed Software

Cisco has released free software updates that address the vulnerability described in this advisory. Prior to deploying software, customers are advised to consult their maintenance providers or check the software for feature set compatibility and known issues that are specific to their environments.

Customers may only install and expect support for feature sets they have purchased. By installing, downloading, accessing, or otherwise using such software upgrades, customers agree to follow the terms of the Cisco software license at http://www.cisco.com/en/US/docs/general/warranty/English/EU1KEN_.html.

Customers with Service Contracts

Customers with contracts should obtain upgraded software through their regular update channels. For most customers, upgrades should be obtained through the Software Navigator on Cisco.com at http://www.cisco.com/cisco/software/navigator.html.

Customers Using Third-Party Support Organizations

Customers with Cisco products that 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 organization for assistance with the appropriate course of action.

The effectiveness of any workaround or fix depends on specific customer situations, such as product mix, network topology, traffic behavior, and organizational mission. Because of the variety of affected products and releases, customers should consult their service providers or support organizations to ensure that any applied workaround or fix is the most appropriate in the intended network before it is deployed.

Customers Without Service Contracts

Customers who purchase directly from Cisco but do not hold a Cisco service contract and customers who make purchases through third-party vendors but are unsuccessful in obtaining fixed software through their point of sale should obtain upgrades by contacting the Cisco Technical Assistance Center (TAC):

  • +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 the product serial number available and be prepared to provide the URL of this advisory as evidence of entitlement to a free upgrade. Customers without service contracts should request free upgrades through the TAC.

Refer to Cisco Worldwide Contacts at http://www.cisco.com/en/US/support/tsd_cisco_worldwide_contacts.html for additional TAC contact information, including localized telephone numbers, instructions, and e-mail addresses for support in various languages.

Exploitation and Public Announcements

The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.

This vulnerability was found internally by Cisco during testing.

Status of This Notice: Final

THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.

A stand-alone copy or Paraphrase of the text of this document that omits the distribution URL in the following section is an uncontrolled copy, and may lack important information or contain factual errors.


Distribution

This advisory is posted on Cisco Security Intelligence Operations at the following link:

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120926-bgp

Additionally, a text version of this advisory is clear signed with the Cisco PSIRT PGP key and circulated among the following e-mail addresses:

  • 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

Future updates of this advisory, if any, will reside on Cisco.com but may not be announced on mailing lists. Users can monitor this advisory's URL for any updates.


Revision History

Revision 1.1 2012-October-04 Added mVPN MDT note in the "Vulnerable Products" section.
Revision 1.0 2012-September-26 Initial public release

Cisco Security Procedures

Complete information about reporting security vulnerabilities in Cisco products, obtaining assistance with security incidents, and registering to receive security information from Cisco is available on Cisco.com at http://www.cisco.com/web/about/security/psirt/security_vulnerability_policy.html. This web page includes instructions for press inquiries regarding Cisco Security Advisories. All Cisco Security Advisories are available at http://www.cisco.com/go/psirt.


Download this document (PDF)
 Download OVAL
View Printable Version