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Cisco Security Advisory

Cisco IOS Software Processing of SAA Packets

Advisory ID: cisco-sa-20030515-saa

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20030515-saa

Revision 1.0

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


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 IOSĀ® 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://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20030515-saa

Affected Products

Vulnerable 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).

Major Release

Vulnerable Releases

12.0S

15, 16, 17, 18, 19, 21

12.0SC

15, 16

12.0SL

15, 17, 19

12.0ST

16, 17, 18, 19, 20, 21

12.0SP

19, 20

12.0SX

21

12.1

10, 10a, 11, 11a, 11b, 12, 12a, 12b, 12c, 13, 14, 14.5

12.1E

10, 11b, 11.5

12.1EA

8, 9

12.1EC

10, 10.5

12.1EX

10

12.1EY

10

12.2

6.8a, 7, 7a, 7b, 7c

12.2DA

7, 9.4

12.2S

9, 10.5

Products Confirmed Not Vulnerable

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

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.

Vulnerability Scoring Details

Cisco has not provided scores for the vulnerabilities in this advisory based on the Common Vulnerability Scoring System (CVSS). At the time of original publication, CVSS scoring in Cisco Security publications had not been adopted.

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

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/web/about/security/intelligence/ios-ref.html.

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

Major Release

Description or Platform

Availability of Repaired Releases*

Affected Earlier Releases

Rebuild

Interim**

Maintenance

11.1 and earlier, all variants

Numerous

Not vulnerable

Affected 11.2-Based Releases

Rebuild

Interim**

Maintenance

11.2 variants

Numerous

Not vulnerable

Affected 11.3-Based Releases

Rebuild

Interim**

Maintenance

11.3 variants

Numerous

Not vulnerable

Affected 12.0-Based Releases

Rebuild

Interim**

Maintenance

12.0S

Core/ISP Support: GSR, RSP, c7200, Cat6000

12.0(21)S3

12.0(21.03)S

 

12.0SC

Cable/Broadband ISP: ubr7200

Not planned

Migrate to 12.1EC release

12.0SL

10000 ESR: c10k

If using Pre1 card, then migrate to 12.0ST or 12.0S.

For Pre card the date is not yet determined.

12.0SP

c10720

12.0(20)SP3

12.0(20.04)SP2

 

12.0ST

MPLS/Tag Switching, GSR 12000, 7200, 7500

12.0(19)ST5

12.0(21)ST2

   

12.0SX

Short-lived early deployment release 10000 ESR: c10k

To be determined

12.0SY

   

12.0(21.03)SY

12.0(22)SY

12.0WC

Short-lived early deployment release for 2900XL and 3500XL

12.0(5)WCa

   

12.0XE

Short-lived early deployment release

Not planned

Migrate to 12.2 release or later

Affected 12.1-Based Releases

Rebuild

Interim**

Maintenance

12.1

General Deployment (GD) candidate: all platforms

 

12.1(18.1)

12.1(18)

12.1E

Core/ISP Support: GSR, RSP, c7200

 

12.1(12.5)E

12.1(13)E

12.1EA

Catalyst 2950

12.1(8)EA1c

   

12.1EC

Early Deployment (ED): ubr7200, UBR Headend platforms

 

12.1(12c)EC

 

12.1EW

Early Deployment release, limited platforms

   

12.1(11b)EW

12.1EW

Early Deployment release, limited platforms

   

12.1(11b)EW(0.46)

12.1EX

Catalyst 6000

   

12.1(11b)EX

12.1XF

Short-lived early deployment release

Not planned Migrate to 12.1(5)T or later

12.1XG

Short-lived early deployment release

Not planned Migrate to 12.1(1)T or later

12.1YB

Short-lived early deployment release

Not planned Migrate to 12.1(2)T or later

12.1YC

Short-lived early deployment release

Not planned Migrate to 12.1(4)T or later

Affected 12.2-Based Releases

Rebuild

Interim**

Maintenance

12.2

General Deployment (GD) candidate: all platforms

 

12.2(10.4)

12.2(10)

12.2(4)B

Early Deployment for 6400, 7200 and 7400

 

12.2(13.3)B

 

12.2BC

Early Deployment for uBR7000 and uBR10000

To be determined

12.2BY

Early Deployment release

Not planned

Migrate to 12.2B releases

12.2BZ

Early Deployment release

   

12.2(15)BZ

12.2DA

Early deployment release xDSL support: 6100, 6200

 

12.2(11.4)DA

12.2(12)DA

12.2MB

Early deployment release for 2600 and 7500

12.2(4)MB5

   

12.2S

Core ISP support

 

12.2(11.1)S

 

12.2XC

Early deployment release

12.2(1a)XC5

   

12.2XD

ICS7750/820/soho70

Not planned

Migrate to 12.2(8)YN or later

12.2XE

806, 828, soho78

Not planned

Migrate to 12.2(8)T or later

12.2XH

1700 820/800/soho70

Not planned

Migrate to 12.2(8)T or later

12.2XI

820/soho

Not planned

Migrate to 12.2(12)T or later

12.2XJ

1700

Not planned

Migrate to 12.2(4)YB or later

12.2XK

820/soho

   

12.2(2)XK3

12.2XL

1700 820/800/soho70

   

12.2(4)XL5

12.2XM

Short-lived early deployment release

Not planned

Migrate to 12.2(8)YB or later

12.2YA

Short-lived early deployment release

12.2(4)YA3

   

12.2YB

Short-lived early deployment release

Not planned

Migrate to 12.2(8)YB or later

12.2YC

Short-lived early deployment release

12.2(4)YC4

   

12.2YF

Cisco Packet Data Serving Node ics7700

Release date to be decided

12.2YG

Short-lived early deployment release

   

12.2(4)YG

12.2YH

Short-lived early deployment release

   

12.2(4)YH

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 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.

Obtaining Fixed Software

Cisco has released free software updates that address these vulnerabilities. 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/en/US/docs/general/warranty/English/EU1KEN_.html , or as otherwise set forth at Cisco.com Downloads 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, 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 agreements 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 do not hold a Cisco service contract, and customers who purchase through third-party vendors but are unsuccessful in obtaining fixed software through their point of sale should acquire 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

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

Refer to http://www.cisco.com/en/US/support/tsd_cisco_worldwide_contacts.html for additional TAC contact information, including 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.

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 will be posted on Cisco's worldwide website at http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20030515-saa

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

Revision 1.0

2003- May-15, 15:00 UTC (GMT)

Initial public release.

Revision 1.1

2003-December-12

Changed Router(config)#ip access-group 101 in to Router(config-if)#ip access-group 101 in in the Exploitation and Public Announcements section.

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.


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