Products & Services

Document ID: 42744

Revision Numeral 1.1

For Public Release 2003 May 15 15:00 UTC (GMT)

Contents

Summary
Affected Products
Details
Impact
Software Versions and Fixes
Obtaining Fixed Software
Workarounds
Exploitation and Public Announcements
Status of This Notice: FINAL
Distribution
Revision History
Cisco Security Procedures

Summary

The Service Assurance Agent (SAA) is the new name for the Response Time Reporter (RTR) feature.

The router is vulnerable only if the RTR responder is enabled. When the router receives a malformed RTR packet, it will crash. RTR is disabled by default. Although RTR was introduced in Cisco IOS® Software Release 11.2, only the following main releases are vulnerable:

• 12.0S, SC, ST, SL, SP, SX
  
• 12.1, E, EA, EC, EX, EY
  
• 12.2, DA, S
  

For the complete list please see the Software Versions and Fixes section.

No other Cisco product is vulnerable.

There is no workaround short of disabling the RTR responder. It is possible to mitigate the vulnerability by applying the access control list (ACL) on the router.

This advisory is available at http://www.cisco.com/warp/public/707/cisco-sa-20030515-saa.shtml.

Affected Products

This vulnerability affects the following main Cisco IOS Software releases (some X releases are also affected, and those details are in the Software Version and Fixes section).

No other Cisco products are affected.

Details

The RTR feature allows you to monitor network performance, network resources, and applications by measuring response times and availability. With this feature you can perform troubleshooting, problem notifications, and problem analysis based on response time reporter statistics.

A router is vulnerable only if the RTR responder is enabled. In order to verify this, check the router's configuration. Execute the following command while logged on a router:

Router>show rtr responder
     RTR Responder is: Enabled
     Number of control messages received: 0 Number of errors: 0 
     Recent sources:
     Recent error sources:

If you notice the line "RTR Responder is: Enabled," then you are vulnerable.

Alternatively, you can use this procedure:

Router>show ip socket
     show ip socket
     Proto    Remote      Port      Local       Port  In Out Stat TTY OutputIF
     ....
      17 0.0.0.0             0 10.0.0.1         1967   0   0   89   0

If you notice a line as in the example above where the router is listening to the port 1967, then you are vulnerable.

For Cisco IOS Software, this vulnerability is documented as two Cisco Bug IDs: CSCdx17916 and CSCdx61997.

Impact

By sending malformed RTR packets, it is possible to crash the router.

Software Versions and Fixes

Each row of the Cisco IOS software table (below) 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 (the "First Fixed Release") and the anticipated date of availability for each are listed in the "Rebuild," "Interim," and "Maintenance" columns. 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. The release should be upgraded at least to the indicated release or a later version (greater than or equal to the First Fixed Release label). When selecting a release, keep in mind the following definitions.

• Maintenance - The most heavily tested, stable, and highly recommended release of a release train in any 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 repair the vulnerability.
  
• Interim - Built at regular intervals between maintenance releases and receives less testing. Interims should be selected only if there is no other suitable release that addresses the vulnerability. Interim images should be upgraded to the next available maintenance release as soon as possible. Interim releases are not available through manufacturing, and usually they are not available for customer download from http://www.cisco.com without prior arrangement with the Cisco TAC.
  

In all cases, customers should exercise caution to confirm that the devices to be upgraded contain sufficient memory and that current hardware and software configurations will continue to be supported properly by the new software release. If the information is not clear, contact the Cisco TAC for assistance as shown in the Obtaining Fixed Software section below.

More information on Cisco IOS software release names and abbreviations is available at http://www.cisco.com/warp/public/620/1.html.

The fixes will be available at the Software Center located at http://www.cisco.com/tacpage/sw-center/.

Obtaining Fixed Software

Cisco is offering free software upgrades to remedy this vulnerability for all affected customers. Customers may only install and expect support for the feature sets they have purchased.

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 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 assistance with the upgrade, which should be free of charge.

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). In those cases, customers may only upgrade to a later version of the same release as indicated by the applicable row in the Software Versions and Fixes table.

Cisco 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
  

See 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.

Please 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.

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

Workarounds

There is no workaround short of disabling the RTR responder. It is possible to mitigate the vulnerability by applying the ACL on the router.

If you want to disable the RTR, you need to execute the following commands:

Router#conf t
     Enter configuration commands, one per line.  End with CNTL/Z.
     Router(config)#no rtr responder
     Router(config)#exit
     Router#copy running-config startup-config

If you want to block all offending packets on your network edge, then you should create an ACL, or modify an existing one, to contain an entry resembling:

Router#conf t
     Enter configuration commands, one per line.  End with CNTL/Z.
     Router(config)#access-list 101 deny udp any any eq 1967
     Router(config)#interface eth0
     Router(config)#ip access-group 101 in

In this example the interface eth0 is assumed to be facing toward the network edge. You will have to substitute it for the correct interface on your router.

This will prevent any packet that is destined to the port 1967/UDP from entering your network. If you need to enable these packets to traverse your network, then the ACL must exclude only your internal routers.

In addition to filtering packets at the network edge, you may apply filtering on the device itself and permit packets only from known good sources. This will contribute to the overall mitigation of this issue.

Router#conf t
     Enter configuration commands, one per line.  End with CNTL/Z.
     Router(config)#access-list 101 permit udp 10.0.0.1 10.0.0.10 eq 1967
     Router(config)#access-list 101 deny udp any 10.0.0.10 eq 1967
     Router(config)#interface eth0
     Router(config-if)#ip access-group 101 in

In this example, 10.0.0.1 is the legitimate source and 10.0.0.10 is the address of the router itself.

Exploitation and Public Announcements

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

Status of This Notice: FINAL

This is a final notice. Although Cisco cannot guarantee the accuracy of all statements in this advisory, all of the facts have been checked to the best of our ability. Cisco does not anticipate issuing updated versions of this advisory unless there is some material change in the facts. Should there be a significant change in the facts, Cisco may update this advisory.

A stand-alone copy or paraphrase of the text of this security advisory 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 will be posted on Cisco's worldwide website at http://www.cisco.com/warp/public/707/cisco-sa-20030515-saa.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
  
• bugtraq@securityfocus.com
  
• full-disclosure@lists.netsys.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 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

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.