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Cisco IOS BGP Attribute Corruption Vulnerability

Advisory ID: cisco-sa-20010510-ios-bgp-attr

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20010510-ios-bgp-attr

Revision 1.1

For Public Release 2001 May 10 15:00  UTC (GMT)


Summary

A Border Gateway Protocol (BGP) UPDATE contains Network Layer Reachability Information (NLRI) and attributes that describe the path to the destination. An unrecognized transitive attribute can cause failures in Cisco IOS routers, ranging from a crash upon receipt of the unrecognized transitive attribute, to a later failure upon attempt to clear the unrecognized transitive attribute. Specific but common configurations are affected, and described below. The failure was discovered because of a malfunction in the BGP implementation of another vendor. There is no workaround. Affected customers are urged to upgrade to fixed code.

This vulnerability has been assigned Cisco bug ID CSCdt79947.

The complete text of this advisory will be located at http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20010510-ios-bgp-attr

Affected Products

Vulnerable Products

Configurations including BGP4 Prefix Filtering with Inbound Route Maps are vulnerable. BGP with prefix inbound routemap filtering was introduced in Cisco IOSĀ® Software version 11.2 The following versions of Cisco IOS Software are affected and listed in the table below: 11.CC and its derivatives, 11.2 and its derivaties, 11.3, 11.3T, 12.0, 12.0S and special branches taken out of 12.0 are all affected. The versions of Cisco IOS Software based on 12.1, 12.0(5)T, 12.2, 12.0ST, and 12.1(E) are not affected. The following products are affected if they run a Cisco IOS software release that has the defect. To determine if a Cisco product is running an affected IOS, log in to the device and issue the show version command. Cisco IOS software will identify itself as "Internetwork Operating System Software" or "IOS (tm)" software and will display a version number. Other Cisco devices either will not have the show version command, or will give different output. Compare the version number obtained from the router with the versions presented in the Software Versions and Fixes section below.

Cisco devices that may be running with affected Cisco IOS software releases include:

  • Cisco routers in the AGS/MGS/CGS/AGS+, IGS, RSM, 800, ubr900, 1000, 1400, 1500, 1600, 1700, 2500, 2600, 3000, 3600, 3800, 4000, 4500, 4700, AS5200, AS5300, AS5800, 6400, 7000, 7200, ubr7200, 7500, and 12000 series.

Products Confirmed Not Vulnerable

Cisco devices that may be running Cisco IOS Software, but do NOT support BGP and are therefore not vulnerable include:

  • Most recent versions of the LS1010 ATM switch.
  • The Catalyst 2900XL LAN switch only if it is running IOS.
  • The Catalyst 1900, 2800, 2900, 3000, and 5000 series LAN switches.
  • The Cisco DistributedDirector.

If you are not running Cisco IOS software, you are not affected by this vulnerability. If you are not running BGP, you are not affected by this vulnerability.

Cisco products that do not run Cisco IOS software and are not affected by this defect include, but are not limited to:

  • 700 series dialup routers (750, 760, and 770 series) are not affected.
  • The Catalyst 6000 is not affected if it is not running IOS.
  • WAN switching products in the IGX and BPX lines are not affected.
  • The MGX (formerly known as the AXIS shelf) is not affected.
  • No host-based software is affected.
  • The Cisco PIX Firewall is not affected.
  • The Cisco LocalDirector is not affected.
  • The Cisco Cache Engine is not affected.

No other Cisco products are currently known to be affected by these vulnerabilities.

Details

A Border Gateway Protocol (BGP) UPDATE contains Network Layer Reachability Information (NLRI) and attributes that describe the path to the destination. Each path attribute is a type, length, value (TLV) object. This failure occurs as a result of memory corruption and only in configurations using specific inbound route filtering. The failure was discovered because of a malfunction in the BGP implementation of another vendor. There is no workaround.

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 .


Impact

The vulnerability can be exercised repeatedly, affecting core routers, creating widespread network outages. This vulnerability can only be exercised in configurations that include both BGP and inbound route filtering on affected software.

Software Versions and Fixes

The following table summarizes the Cisco IOS software releases that are known to be affected, and the earliest estimated dates of availability for the recommended fixed versions. Dates are always tentative and subject to change.

Each row of the table describes a release train and the platforms or products for which it is intended. If a given release train is vulnerable, then the earliest possible releases that contain the fix and the anticipated date of availability for each are listed in the "Rebuild", "Interim", and "Maintenance" columns. A device running any release in the given train that is earlier than the release in a specific column (less than the earliest fixed release) is known to be vulnerable, and it should be upgraded at least to the indicated release or a later version (greater than the earliest fixed release label).

When selecting a release, keep in mind the following definitions:

  • Maintenance
    Most heavily tested and highly recommended release of any label in a given row of the table.
  • Rebuild
    Constructed from the previous maintenance or major release in the same train, it contains the fix for a specific defect. Although it receives less testing, it contains only the minimal changes necessary to effect the repair.
  • Interim
    Built at regular intervals between maintenance releases and receive less testing. Interims should be selected only if there is no other suitable release that addresses the vulnerability, and interim images should be upgraded to the next available maintenance release as soon as possible. Interim releases are not available via manufacturing, and usually they are not available for customer download from CCO without prior arrangement with the Cisco TAC.

In the table below, the logical superseding software is recommended when there is no rebuild or maintenance planned for a specific software release. Customers should verify that planned upgrades will meet their requirements. For further details, see the IOS Release Notes for each Cisco IOS Train. http://www.cisco.com/univercd/cc/td/doc/product/software/index.htm. 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 TAC for assistance as shown later in this notice.

More information on Cisco IOS Software release names and abbreviations is available at http://www.cisco.com/en/US/products/sw/iosswrel/tsd_products_support_category_home.html.

Train

Description of Image or Platform

Availability of Fixed Releases*

11.0-based Releases

Rebuild

Interim

Maintenance

11.0

Major GD release for all platforms

Not vulnerable

11.1-based Releases

Rebuild

Interim

Maintenance

11.1

Major release for all platforms

Not vulnerable

11.1AA

ED release for access servers: 1600, 3200, and 5200 series.

Not vulnerable

11.1CA

Platform-specific support for 7500, 7200, 7000, and RSP

End of Engineering

Not scheduled

11.1CC

ISP train: added support for FIB, CEF, and NetFlow on 7500, 7200, 7000, and RSP

11.1(36)CC2

2001-May-29

11.1CT

Added support for Tag Switching on 7500, 7200, 7000, and RSP

End of Engineering

Upgrade recommended to 12.0ST

11.1IA

Distributed Director only

Not Vulnerable

11.2-based Releases

Rebuild

Interim

Maintenance

11.2

Major release, general deployment

End of Engineering

Not scheduled

11.2BC

Platform-specific support for IBM networking, CIP, and TN3270 on 7500, 7000, and RSP

End of Engineering

Upgrade recommended to 12.1(8)

11.2F

Feature train for all platforms

End of Engineering

Upgrade recommended

11.2GS

Early deployment release to support 12000 GSR

End of Engineering

Upgrade recommended to 12.0(17)S

11.2P

New platform support

End of Engineering

Upgrade recommended to 12.0(17)

11.2SA

Catalyst 2900XL switch only

Not vulnerable

11.2WA3

LightStream 1010 ATM switch

Not vulnerable

11.2(4)XA

Initial release for the 1600 and 3600

End of Engineering

Upgrade recommended

11.2(9)XA

Initial release for the 5300 and digital modem support for the 3600

End of Engineering

Upgrade recommended

11.3-based Releases

Rebuild

Interim

Maintenance

11.3

Major release for all platforms

End of Engineering

Upgrade recommended to 12.0(17)

11.3AA

ED for dial platforms and access servers: 5800, 5200, 5300, 7200

End of Engineering

Upgrade recommended to 12.0(17)

11.3DA

Early deployment train for ISP DSLAM 6200 platform

End of Engineering

Upgrade recommended to 12.1DA

11.3DB

Early deployment train for ISP/Telco/PTT xDSL broadband concentrator platform, (NRP) for 6400

End of Engineering

Upgrade recommended to 12.1DB

11.3HA

Short-lived ED release for ISR 3300 (SONET/SDH router)

End of Engineering

Upgrade recommended to 12.0

11.3MA

MC3810 functionality only

Not available

Not scheduled

11.3NA

Voice over IP, media convergence, various platforms

End of Engineering

Upgrade recommended to 12.1

11.3T

Early deployment major release, feature-rich for early adopters

End of Engineering

Upgrade recommended to 12.0(17)

11.3WA4

Multilayer Switching and Multiprotocol over ATM functionality for Catalyst 5000 RSM, 4500, 4700, 7200, 7500, LightStream 1010

End of Engineering

Upgrade recommended

11.3(2)XA

Introduction of ubr7246 and 2600

End of Engineering

Upgrade recommended

12.0-based Releases

Rebuild

Interim

Maintenance

12.0

General deployment release for all platforms

   

12.0(17) 2001-Apr-23

12.0DA

xDSL support: 6100, 6200

Unavailable

Upgrade recommended to 12.1DA

12.0DB

Early Deployment (ED) release, which delivers support for the Cisco 6400 Universal Access Concentrator (UAC) for Node Switch Processor (NSP)

Unavailable

Upgrade recommended to 12.1DB

12.0DC

Early Deployment (ED) release, which delivers support for the Cisco 6400 Universal Access Concentrator (UAC) for Node Route Processor (NRP)

Unavailable

Upgrade recommended to 12.1DC

12.0S

Core/ISP support: GSR, RSP, c7200

12.0(15)S3, 12.0(16)S1

12.0(16.06)S

12.0(17)S

2001-April-23 2001-April-30

 

2001-May-07

12.0SC

Cable/broadband ISP: ubr7200

Not vulnerable

12.0SL

10000 ESR: c10k

Not vulnerable

12.0ST

Cisco IOS software Release12.0ST is an early deployment (ED) release for the Cisco 7200, 7500/7000RSP and 12000 (GSR) series routers for Service Providers (ISPs).

Not vulnerable

12.0T

Early Deployment(ED): VPN, Distributed Director, various platforms

   

12.0(5)T

12.0W5

Catalyst switches: cat2948g-l3, cat4232

12.0(10)W5(18g) 2001-Apr-20

   

cat8510c, cat8540c, c6msm, ls1010, cat8510m, cat8540m, c5atm

   

12.0(16)W5(21) 2001-May-21

12.0WT

Catalyst switches: cat4840g

Not vulnerable

12.0XA

Early Deployment (ED): limited platforms

Unavailable

Upgrade recommended to 12.1

12.0XB

Short-lived early deployment release

Unavailable

Upgrade recommended to 12.1

12.0XC

Early Deployment (ED): limited platforms

Unavailable

Upgrade recommended to 12.1

12.0XD

Early Deployment (ED): limited platforms

Unavailable

Upgrade recommended to 12.1

12.0XE

Early Deployment (ED): limited platforms

Not Vulnerable

12.0XF

Early Deployment (ED): limited platforms

Unavailable

Upgrade recommended to 12.1

12.0XG

Early Deployment (ED): limited platforms

Unavailable

Upgrade recommended to 12.1

12.0XH

Early Deployment (ED): limited platforms

Unavailable

Upgrade recommended to 12.1

12.0XI

Early Deployment (ED): limited platforms

Unavailable

Upgrade recommended to 12.1

12.0XJ

Early Deployment (ED): limited platforms

Unavailable

Upgrade recommended to 12.1

12.0XK

Early Deployment (ED): limited platforms

Not vulnerable

12.0XL

Early Deployment (ED): limited platforms

Not vulnerable

12.0XM

Short-lived early deployment release

Not vulnerable

12.0XN

Early Deployment (ED): limited platforms

Not vulnerable

12.0XP

Early Deployment (ED): limited platforms

Not vulnerable

12.0XQ

Short-lived early deployment release

Not vulnerable

12.0XR

Short-lived early deployment release

Not vulnerable

12.0XS

Short-lived early deployment release

Not vulnerable

12.0XU

Early Deployment (ED): limited platforms

Not vulnerable

12.0XV

Short-lived early deployment release

Not vulnerable

12.1-based and Later Releases

Rebuild

Interim

Maintenance

12.1

General deployment release for all platforms

Not vulnerable

Notes

* All dates are estimated and subject to change.

** Interim releases are subjected to less rigorous testing than regular maintenance releases, and may have serious bugs.

Workarounds

There are no known workarounds for this vulnerablity. Please upgrade to fixed versions.

Obtaining Fixed Software

Cisco has made free software available to address this vulnerability for affected customers. Prior to deploying software, customers should consult their maintenance provider or check the software for feature set compatibility and known issues specific to their environment.

Customers may only install and expect support for the feature sets they have purchased. By installing, downloading, accessing or otherwise using such software upgrades, customers agree to be bound by the terms of Cisco's software license terms found at http://www.cisco.com/public/sw-license-agreement.html, or as otherwise set forth at Cisco.com Downloads at http://www.cisco.com/public/sw-center/sw-usingswc.shtml.

Do not contact either "psirt@cisco.com" or "security-alert@cisco.com" for software upgrades.

Customers with Service Contracts

Customers with contracts should obtain upgraded software through their regular update channels. For most customers, this means that upgrades should be obtained through the Software Center on Cisco's worldwide website at http://www.cisco.com.

Customers using Third Party Support Organizations

Customers whose Cisco products are provided or maintained through prior or existing agreement with third-party support organizations such as Cisco Partners, authorized resellers, or service providers should contact that support organization for guidance and assistance with the appropriate course of action in regards to this advisory.

The effectiveness of any workaround or fix is dependent on specific customer situations such as product mix, network topology, traffic behavior, and organizational mission. Due to the variety of affected products and releases, customers should consult with their service provider or support organization to ensure any applied workaround or fix is the most appropriate for use in the intended network before it is deployed.

Customers without Service Contracts

Customers who purchase direct from Cisco but who do not hold a Cisco service contract and customers who purchase through third-party vendors but are unsuccessful at obtaining fixed software through their point of sale should get their upgrades by contacting the Cisco Technical Assistance Center (TAC). TAC contacts are as follows.

  • +1 800 553 2447 (toll free from within North America)
  • +1 408 526 7209 (toll call from anywhere in the world)
  • e-mail: tac@cisco.com

Have your product serial number available and give the URL of this notice as evidence of your entitlement to a free upgrade. Free upgrades for non-contract customers must be requested through the TAC.

Refer to http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml for additional TAC contact information, including special localized telephone numbers and instructions and e-mail addresses for use in various languages.

Exploitation and Public Announcements

Cisco has had no reports of malicious exploitation of this vulnerability. The failure was discovered because of a malfunction in the BGP implementation of another vendor, which caused a series of crashes that led to the identification of this issue.

Cisco knows of no public announcements of this vulnerability before the date of this notice.

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 notice will be posted on Cisco's Worldwide Web site at http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20010510-ios-bgp-attr. 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
  • bugtraq@securityfocus.com
  • firewalls@lists.gnac.com
  • first-teams@first.org (includes CERT/CC)
  • cisco@spot.colorado.edu
  • cisco-nsp@puck.nether.net
  • comp.dcom.sys.cisco
  • Various internal Cisco mailing lists

Future updates of this advisory, if any, will be placed on Cisco's Worldwide Web server, 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 1.1

2001-November-29

Made changes to upgrade recommendations for some IOS versions

Revision 1.0

2001-May-10

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 Web site at http://www.cisco.com/web/about/security/psirt/security_vulnerability_policy.html. This includes instructions for press inquiries regarding Cisco security notices.