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Cisco Security Advisory

Cisco IOS Software IP Service Level Agreement Vulnerability

Advisory ID: cisco-sa-20110928-ipsla

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20110928-ipsla

Revision 2.1

Last Updated  2012 September 21 19:19  UTC (GMT)

For Public Release 2011 September 28 16:00  UTC (GMT)


Summary

The Cisco IOS IP Service Level Agreement (IP SLA) feature contains a denial of service (DoS) vulnerability. The vulnerability is triggered when malformed UDP packets are sent to a vulnerable device. The vulnerable UDP port numbers depend on the device configuration. Default ports are not used for the vulnerable UDP IP SLA operation or for the UDP responder ports.

Cisco has released free software updates that address this vulnerability.

This advisory is posted at http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20110928-ipsla.

Note: The September 28, 2011, Cisco IOS Software Security Advisory bundled publication includes ten Cisco Security Advisories. Nine of the advisories address vulnerabilities in Cisco IOS Software, and one advisory addresses vulnerabilities in Cisco Unified Communications Manager. 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 September 2011 Bundled Publication.

Individual publication links are in "Cisco Event Response: Semiannual Cisco IOS Software Security Advisory Bundled Publication" at the following link:

http://www.cisco.com/web/about/security/intelligence/Cisco_ERP_sep11.html


Affected Products

Vulnerable Products

Cisco devices that are running Cisco IOS Software are vulnerable when they are configured for IP SLA, either as responders or as originators of vulnerable IP SLA operations.

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 shows output from a device that runs a Cisco IOS Software image:

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 the white paper Cisco IOS and NX-OS Software Reference Guide available at: http://www.cisco.com/web/about/security/intelligence/ios-ref.html.

Products Confirmed Not Vulnerable

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

Details

IP SLA is an embedded agent in Cisco IOS Software designed to measure and monitor common network performance metrics like jitter, latency (delay), and packet loss.

The vulnerability that is described in this document is triggered by  malformed IP SLA packets sent to the vulnerable device and port. A vulnerable device can be an IP SLA responder or the source device of a vulnerable IP SLA operation.

This vulnerability is documented in Cisco bug ID CSCtk67073 ( registered customers only) and has been assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2011-3272.

Vulnerable IP SLA Responder Configurations

A device configured either as an IP SLA general responder or a permanent IP SLA UDP responder is vulnerable.

The general responder processes IP SLA control protocol packets on UDP port 1967 and then may dynamically open vulnerable UDP ports according to the IP SLA operations requested using the control protocol. The configuration for a general responder is as follows:

ip sla responder 

The IP SLA UDP permanent responder is also vulnerable. An example configuration is as follows:

ip sla responder udp-echo port 300

There is no default UDP port number for the UDP permanent responder

Alternatively, both the general responder and the permanent responder can be identified with the show ip sla responder command. The general responder is vulnerable when it has been enabled. The permanent responder is vulnerable only when it has been enabled and the "udpEcho Responder" is present. In the Following example, the general responder is not vulnerable because it has not been enabled but the permanent responder is vulnerable because it has been enabled with a UDP echo responder:

Router# show ip sla responder
        General IP SLA Responder on Control port 1967
General IP SLA Responder is: Disabled

        Permanent Port IP SLA Responder
Permanent Port IP SLA Responder is: Enabled

udpEcho Responder: 
  IP Address             Port
  0.0.0.0                 300

Vulnerable IP SLA Source Device Configurations

An IP SLA source device is a Cisco IOS device that has at least one IP SLA operation configured. To be vulnerable a probe originator needs to have at least one scheduled probe that uses either of the following IP SLA operations:

  • udp-jitter probe
  • udp-echo

A vulnerable IP SLA source device configuration includes all the following commands:

  • An ip sla global configuration command to define an IP SLA operation
  • Either a udp-echo or a udp-jitter IP SLA configuration command
  • An ip sla schedule global configuration command that activates one of the probes that uses a vulnerable IP SLA operation

The following examples show a source device that is configured for IP SLA UDP echo and UDP jitter probes:

ip sla 201
 udp-echo 192.168.134.21 201
ip sla schedule 201 start-time now

ip sla 301
 udp-jitter 192.168.134.121 122
ip sla schedule 301 start-time now

The destination UDP ports for the probes need to be configured. If the source UDP port is not configured an available port number will be used when the probe is started. A device that originates a vulnerable operation will be vulnerable on the source UDP ports of the probe and a responder will be vulnerable on the destination UDP port used for the probe.

IP SLA probes can be configured using Simple Network Management Protocol (SNMP). In that case, by default, the output of the show running-config command will not include the IP SLA probe configuration. The show ip sla configuration command can be used to verify whether a probe has been configured either by the command line or via SNMP.

Router# show ip sla configuration | include operation
Type of operation to perform: udp-jitter

Vulnerability Scoring Details

Cisco has provided scores for the vulnerability 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 .

CSCtk67073 IP SLA Memory Corruption Vulnerability

Calculate the environmental score of CSCtk67073

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 the vulnerability described in this document may result in the reload of a vulnerable device. Repeated exploitation could result in a DoS condition.

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.

Additionally, the Cisco IOS Software Checker is available on the Cisco Security Intelligence Operations (SIO) portal at http://tools.cisco.com/security/center/selectIOSVersion.x. It provides several features for checking which Security Advisories affect specified versions of Cisco IOS Software.

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 For This Advisory column. The First Fixed Release for All Advisories in the September 2011 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.

Major Release

     Availability of Repaired Releases

Affected 12.0-Based Releases

First Fixed Release

First Fixed Release for All Advisories in the September 2011 Bundled Publication

There are no affected 12.0-based releases

Affected 12.1-Based Releases

First Fixed Release

First Fixed Release for All Advisories in the September 2011 Bundled Publication

There are no affected 12.1-based releases

Affected 12.2-Based Releases

First Fixed Release

First Fixed Release for All Advisories in the September 2011 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 September 2011 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 September 2011 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 September 2011 Bundled Publication

There are no affected 15.0-based releases

Affected 15.1-Based Releases

First Fixed Release

First Fixed Release for All Advisories in the September 2011 Bundled Publication

15.1EY

Not vulnerable

Vulnerable; contact your support organization per the instructions in the Obtaining Fixed Software section of this advisory.

15.1GC

Vulnerable; first fixed in Release 15.1T

Vulnerable; first fixed in Release 15.1T

15.1M

Not vulnerable

15.1(4)M2; Available on 30-SEP-11

15.1MR

Not vulnerable

Vulnerable; contact your support organization per the instructions in the Obtaining Fixed Software section of this advisory.

15.1S

15.1(2)S

Cisco IOS XE devices: Please see Cisco IOS-XE Software Availability

15.1(2)S2

15.1(3)S

Cisco IOS XE devices: Please see Cisco IOS-XE Software Availability

15.1T

15.1(1)T3

15.1(2)T4

15.1(3)T2

15.1(1)T4; Available on 08-DEC-11

15.1(2)T4

15.1(3)T2

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 September 2011 Bundled Publication

There are no affected 15.2-based releases

Cisco IOS XE Software

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

Cisco IOS XE Release

First Fixed Release

First Fixed Release for All Advisories in the September 2011 Bundled Publication

2.1.x

Vulnerable; migrate to 3.3.2S or later

Vulnerable; migrate to 3.3.2S or later

2.2.x

Vulnerable; migrate to 3.3.2S or later

Vulnerable; migrate to 3.3.2S or later

2.3.x

Vulnerable; migrate to 3.3.2S or later

Vulnerable; migrate to 3.3.2S or later

2.4.x

Vulnerable; migrate to 3.3.2S or later

Vulnerable; migrate to 3.3.2S or later

2.5.x

Vulnerable; migrate to 3.3.2S or later

Vulnerable; migrate to 3.3.2S or later

2.6.x

Vulnerable; migrate to 3.3.2S or later

Vulnerable; migrate to 3.3.2S or later

3.1.xS

Vulnerable; migrate to 3.3.2S or later

Vulnerable; migrate to 3.3.2S or later

3.1.xSG

Vulnerable; migrate to 3.2.0SG or later

Vulnerable; migrate to 3.2.0SG or later

3.2.xS

Vulnerable; migrate to 3.3.2S or later

Vulnerable; migrate to 3.3.2S or later

3.2.xSG

Not vulnerable

Not vulnerable

3.3.xS

3.3.0S

3.3.2S

3.4.xS

Not vulnerable

Not vulnerable

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


Workarounds

There are no workarounds for this vulnerability, but there are mitigations that can be deployed on a general IP SLA responder to reduce the exposure to this vulnerability.

General IP SLA Responder Mitigation

For devices that are configured as general responders, a mitigation is to restrict IP SLA control packets on UDP port 1967 that are addressed to the vulnerable device to permit only trusted probe originators to open UDP ports that could be exploited. This can be accomplished using techniques such as Infrastructure Access list or Control Plane Protection.

For devices configured as general responders, mitigation techniques that can be deployed on Cisco devices within the network are available in the Cisco Applied Mitigation Bulletin companion document for this advisory: http://tools.cisco.com/security/center/content/CiscoAppliedMitigationBulletin/cisco-amb-20110928-ipsla.

IP SLA Permanent Responder Mitigation

For the permanent responder, the mitigation is to filter UDP packets addressed to the configured UDP port of each permanent responder to permit packets from the IP addresses of trusted devices.

IP SLA Source Devices Mitigation

For IP SLA source devices, a mitigation is to allow only UDP packets from trusted devices (that is, devices that are the target of IP SLA operations)

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.

This vulnerability was found during Cisco 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 Cisco's worldwide website at:

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20110928-ipsla

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 1.2

2011-Oct-10

Clarify malformed IP SLA packets in Details section.

Revision 1.1

2011-Oct-07

Updated show running-config command nomenclature in Details section

Revision 1.0

2011-Sep-28

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.


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