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Cisco IOS XR MPLS Vulnerabilities

Advisory ID: cisco-sa-20060419-xr

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20060419-xr

Revision 1.0

For Public Release 2006 April 19 15:00  UTC (GMT)


Summary

Multiple Multi Protocol Label Switching (MPLS) related vulnerabilities exist on Cisco IOS® XR. Only systems that are running Cisco IOS XR and configured for MPLS are affected by these vulnerabilities.

Upon successful exploitation a Modular Services Card (MSC) on a Cisco Carrier Routing System 1 (CRS-1) or a Line Card (LC) on a Cisco 12000 series router may reload affecting switched traffic.

Cisco has made free software available to address this vulnerability for affected customers.

This advisory is posted at http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20060419-xr.

Affected Products

This section provides details on affected products.

Vulnerable Products

Only systems that are running Cisco IOS XR and configured for MPLS are affected by this vulnerability.

Systems that are running Cisco IOS XR and configured for MPLS can be identified by the show mpls interfaces command. A sample output of this command on a CRS-1 that is configured for MPLS is given below.

  RP/0/RP1/CPU0:crs1#show mpls interfaces
  Interface                  LDP      Tunnel   Enabled
  -------------------------- -------- -------- --------
  POS0/2/0/0                 Yes      Yes      Yes
  POS0/2/0/1                 No       Yes      Yes
  POS0/2/0/2                 Yes      No       Yes
  POS0/2/0/3                 Yes      Yes      Yes
  GigabitEthernet0/3/1/0     Yes      No       Yes
  GigabitEthernet0/3/1/3     Yes      No       Yes
  POS0/3/0/1                 Yes      Yes      Yes
  TenGigE0/6/0/0             Yes      No       Yes
  RP/0/RP1/CPU0:crs# 

In the above output, the fourth column labeled Enabled identifies MPLS enabled interfaces.

Products Confirmed Not Vulnerable

Cisco IOS XR only runs on CRS-1 or Cisco 12000 series routers. Other Cisco products, including systems that run Cisco IOS are not affected.

Details

Cisco IOS XR Software is a member of the Cisco IOS Software Family that uses a microkernel based distributed operating system infrastructure. Cisco IOS XR runs both on Cisco CRS-1 and Cisco 12000 series routers.

More information on Cisco IOS XR can be found at the following URL:

http://www.cisco.com/en/US/products/ps5845/index.html

Modular Services Cards (MSC), also called the line cards are Layer-3 forwarding engines on Cisco CRS-1. An MSC is paired with a physical layer interface module (PLIM) which provides layer-1 and layer-2 services.

More information on Cisco CRS-1 architecture can be found at the following URL:

http://www.cisco.com/en/US/products/ps5763/index.html

Specific MPLS packets that are switched by a Cisco CRS-1 or a 12000 series system will restart the NetIO process. If the NetIO process is restarted several times consecutively, the line card will reload causing a Denial of Service (DoS) condition for the traffic that is being switched on that line card.

MPLS packets will be forwarded through the MPLS network. Therefore, packets that can trigger this vulnerability can be sent from remote systems that are in the MPLS network. Such packets can not be received on interfaces that are not configured for MPLS.

This vulnerability is addressed by the following Cisco bug IDs:

  • CSCsd15970 -- MSC crash upon receipt of specific MPLS packets
    This bug only affects CRS-1 and does not affect Cisco 12000 series routers that are running Cisco IOS XR.

  • CSCsd55531 -- MPLS packet handling problems
    This bug only affects CRS-1 and does not affect Cisco 12000 series routers that are running Cisco IOS XR.

  • CSCsc77475 -- Line card crash upon receipt of specific MPLS packets
    This bug affects both CRS-1 and Cisco 12000 series routers that are running Cisco IOS XR.


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

Successful exploitation of the vulnerability may result in a reload of the Modular Services Card (MSC) on a CRS-1 or the line cards on a Cisco 12000 series router. Repeated exploitation could result in a sustained DoS attack.

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.

Cisco IOS XR Version

SMU ID

3.2.0

AA01447

3.2.1

AA01446

3.2.2

AA01448

3.2.3 for CRS-1

AA01444

3.2.3 for PRP

AA01451

3.2.4

AA01449

3.2.50

AA01450

3.3

Cisco IOS XR 3.3 is not vulnerable

Workarounds

There is no workaround to mitigate the effects of these vulnerabilities.

Obtaining Fixed Software

Cisco will make free software available to address this vulnerability for affected customers. This advisory will be updated as fixed software becomes available. 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

The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerability described in this advisory.

This vulnerability was reported to Cisco by a customer.

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's worldwide website at :

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20060419-xr

In addition to worldwide web posting, a text version of this notice is clear-signed with the Cisco PSIRT PGP key and is posted to the following e-mail and Usenet news recipients.

  • cust-security-announce@cisco.com
  • first-teams@first.org
  • 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

2006-April-19

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/web/about/security/psirt/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.