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Cisco IOS Software RSVP Denial of Service Vulnerability

Advisory ID: cisco-sa-20120328-rsvp

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120328-rsvp

Revision 1.0

For Public Release 2012 March 28 16:00  UTC (GMT)


Summary

Cisco IOS Software and Cisco IOS XE Software contain a vulnerability in the RSVP feature when used on a device configured with VPN routing and forwarding (VRF) instances. This vulnerability could allow an unauthenticated, remote attacker to cause an interface wedge, which can lead to loss of connectivity, loss of routing protocol adjacency, and other denial of service (DoS) conditions. This vulnerability could be exploited repeatedly to cause an extended DoS condition.

A workaround is available to mitigate this vulnerability.

Cisco has released free software updates that address this vulnerability. This advisory is available at the following link:  http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120328-rsvp

Note: The March 28, 2012, Cisco IOS Software Security Advisory bundled publication includes nine Cisco Security Advisories. Each 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 vulnerabilities in the March 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_mar12.html


Affected Products


Vulnerable Products

Only devices with specific configurations are affected. Cisco devices that are running affected Cisco IOS Software or Cisco IOS XE Software versions are vulnerable when they are configured with RSVP and also have one or more VRF interfaces. A device is vulnerable if both the following criteria are met:

  • At least one VRF is configured without RSVP
  • At least one other interface (physical or virtual), not in the same VRF, is configured with RSVP

Some example scenarios are as follows:

  • RSVP-Traffic Engineering (RSVP-TE) in Multiprotocol Label Switching (MPLS) infrastructures
  • Multi-VRF infrastructures
  • VRF-Lite infrastructures

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

Cisco IOS-XR software is not affected by this vulnerability.

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

Details

Cisco IOS Software and Cisco IOS XE Software contain a vulnerability in the RSVP feature when used on a device configured with VPN routing and forwarding (VRF) instances.  This vulnerability could allow an unauthenticated, remote attacker to cause an interface wedge, which can lead to loss of connectivity, loss of routing protocol adjacency, and other denial of service (DoS) conditions.  This vulnerability could be exploited repeatedly to cause an extended DoS condition.

A device is vulnerable if it is configured with VRF and none of the interfaces in that VRF have RSVP enabled, but any other interface (physical or virtual) does have RSVP enabled.

An attacker with some knowledge of the affected infrastructure could exploit this vulnerability by sending RSVP packets to vulnerable devices. Successful exploitation of the vulnerability could allow an attacker to wedge the receive queue of any RSVP ingress interface.

A workaround is available to mitigate this vulnerability.

In devices that meet the vulnerable configuration criteria, valid RSVP packets could trigger this vulnerability. An attacker with knowledge of the infrastructure could craft valid RSVP packets with set conditions to exploit this vulnerability. Recovery from this interface queue wedge requires a reload of the device.

An interface queue wedge is a class of vulnerability in which certain packets are received and queued by a Cisco IOS router or switch but, due to a processing error, are never removed from the queue.

For more information about queue wedges and a few detection mechanisms that may be used to identify a blocked interface on Cisco IOS Software (including a white paper describing how this condition can be detected using SNMP) see http://blogs.cisco.com/security/comments/cisco_ios_queue_wedges_explained/.

This vulnerability has been documented in Cisco bug ID CSCts80643 (registered customers only) and has been assigned the Common Vulnerabilities and Exposures (CVE) ID CVE-2012-1311.

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


CSCts80643 - Cisco IOS Software RSVP Denial of Service Vulnerability

Calculate the environmental score of CSCts80643

CVSS Base Score - 7.8

Access Vector

Access Complexity

Authentication

Confidentiality Impact

Integrity Impact

Availability Impact

Network

Low

None

None

None

Complete

CVSS Temporal Score - 6.4

Exploitability

Remediation Level

Report Confidence

Functional

Official-Fix

Confirmed

Impact

Successful exploitation of this vulnerability will result in an interface queue wedge, which can lead to loss of connectivity, loss of routing protocol adjacency, and other DoS conditions. This vulnerability could be exploited repeatedly to cause an extended DoS condition.

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 March 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 March 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 March 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 March 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 March 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 March 2012 Cisco IOS Software Security Advisory Bundled Publication
15.0M 15.0(1)M8
15.0(1)M8
15.0MR Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
15.0MRA Not vulnerable
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
15.0S Not vulnerable
Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
15.0(1)S5
Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
15.0SA Not vulnerable
Not vulnerable
15.0SE Not vulnerable
15.0(1)SE1
15.0SG Not vulnerable
Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
15.0(2)SG2
Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
15.0SY 15.0(1)SY1
15.0(1)SY1
15.0XA Vulnerable; First fixed in Release 15.1T
Vulnerable; First fixed in Release 15.1T
15.0XO Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
Affected 15.1-Based Releases First Fixed Release First Fixed Release for All Advisories in the March 2012 Cisco IOS Software Security Advisory Bundled Publication
15.1EY 15.1(2)EY2
15.1(2)EY2
15.1GC 15.1(2)GC2
15.1(2)GC2
15.1M 15.1(4)M3
15.1(4)M3a
15.1(4)M4; Available on 30-MAR-12
15.1MR Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
15.1S 15.1(3)S2
Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
15.1(3)S2
Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
15.1SG Not vulnerable
Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
Not vulnerable
Cisco IOS XE devices: Please see Cisco IOS XE Software Availability
15.1SNG Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
Vulnerable; contact your support organization per the instructions in Obtaining Fixed Software section of this advisory.
15.1SNH Not vulnerable
Not vulnerable
15.1T 15.1(1)T5; Available on 18-MAY-12
15.1(2)T5; Available on 27-APR-12
15.1(3)T3
15.1(3)T3
15.1XB Vulnerable; First fixed in Release 15.1T
Vulnerable; First fixed in Release 15.1T
Affected 15.2-Based Releases First Fixed Release First Fixed Release for All Advisories in the March 2012 Cisco IOS Software Security Advisory Bundled Publication
There are no affected 15.2 based releases
 

Cisco IOS XE Software

Cisco IOS XE Software is affected by the vulnerability that is disclosed in this document.

Cisco IOS XE Software Release First Fixed Release First Fixed Release for All Advisories in the March 2012 Cisco IOS Software Security Advisory Bundled Publication
2.1.x Not vulnerable Vulnerable; migrate to 3.4.2S or later.
2.2.x Not vulnerable Vulnerable; migrate to 3.4.2S or later.
2.3.x Not vulnerable Vulnerable; migrate to 3.4.2S or later.
2.4.x Not vulnerable Vulnerable; migrate to 3.4.2S or later.
2.5.x Not vulnerable Vulnerable; migrate to 3.4.2S or later.
2.6.x Not vulnerable Vulnerable; migrate to 3.4.2S or later.
3.1.xS Not vulnerable Vulnerable; migrate to 3.4.2S or later.
3.1xSG Not vulnerable Vulnerable; migrate to 3.2.2SG or later.
3.2.xS Vulnerable; migrate to 3.4.2S or later. Vulnerable; migrate to 3.4.2S or later.
3.2xSG Not vulnerable 3.2.2SG
3.3.xS Vulnerable; migrate to 3.4.2S or later. Vulnerable; migrate to 3.4.2S or later.
3.3.xSG Not Vulnerable Not Vulnerable
3.4.xS 3.4.2S 3.4.2S
3.5.xS Not vulnerable 3.5.1S
3.6.xS Not vulnerable Not vulnerable

For a mapping of Cisco IOS XE Software releases to Cisco IOS Software releases, refer to Cisco IOS XE 2 Release Notes, Cisco IOS XE 3S Release Notes, and Cisco IOS XE 3SG Release Notes.

Cisco IOS XR Software

Cisco IOS XR Software is not affected by any of the vulnerabilities disclosed in the March 2012 Cisco IOS Software Security Advisory Bundled Publication.

Workarounds

It is possible to mitigate the vulnerability in this advisory by applying the global configuration command ip rsvp listener vrf vrf-name ip-address 0 0 announce, where the IP address is one that does not exist on the device or in the routing tables.

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, or as set forth 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, upgrades should be obtained through the Software Center on Cisco.com at http://www.cisco.com.

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 discovered by Cisco during internal 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 the Cisco Security Intelligence Operations portal at the following link:

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120328-rsvp

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 1.0 2012-March-28 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.