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Cisco Security Advisory

Jabber Extensible Communications Platform and Cisco Unified Presence XML Denial of Service Vulnerability

Advisory ID: cisco-sa-20110928-xcpcupsxml

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

Revision 1.1

Last Updated  2012 July 18 14:37  UTC (GMT)

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

Related Resources:

View related Alert

Summary

A denial of service (DoS) vulnerability exists in Jabber Extensible Communications Platform (Jabber XCP) and Cisco Unified Presence. An unauthenticated, remote attacker could exploit this vulnerability by sending malicious XML to an affected server. Successful exploitation of this vulnerability could cause elevated memory and CPU utilization, resulting in memory exhaustion and process crashes. Repeated exploitation could result in a sustained DoS condition.

There are no workarounds available to mitigate exploitation of this vulnerability.

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

Affected Products

Vulnerable Products

The following versions of Cisco Unified Presence and Jabber Extensible Communications Platform (Jabber XCP) are affected by the vulnerability in this advisory. JabberNow appliances are also affected if they are running a vulnerable version of Jabber XCP software.

Cisco Unified Presence

All versions of Cisco Unified Presence prior to 8.5(4) are affected by the vulnerability in this advisory.

Jabber XCP and JabberNow Appliances

The following Jabber XCP software versions are affected by the vulnerability in this advisory:

Versions

Builds

2.X

All builds

3.X

All builds

4.X

All builds

5.0

All builds

5.1

All builds

5.2

All builds

5.4

Prior to 5.4.0.27581

5.8

Prior to 5.8.1.27561

Note: JabberNow appliances that are running these software versions are also affected by the vulnerability in this advisory.

Determining Cisco Unified Presence Software Versions

To determine the running version of Cisco Unified Presence software, issue the show version active command from the command line interface.

The following example shows Cisco Unified Presence software version 8.6.0:

admin: show version active
Active Master Version: 8.6.0.97041-43

Determining Jabber XCP Software Versions

To determine the running version of Jabber XCP software, find the JABBER_VERSION in the [JABBER_HOME]/var/cache/xcp_vars.sh file.

The following example shows Jabber XCP software version 5.8.1.17421:

JABBER_VERSION=5.8.1.17421

Products Confirmed Not Vulnerable

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

Details

Jabber XCP and Cisco Unified Presence provide an open and extensible platform that facilitates the secure exchange of availability and instant messaging (IM) information.

The XML parsers in Jabber XCP (including JabberNow appliances) and Cisco Unified Presence are vulnerable to the Exponential Entity Expansion attack. This attack is also known as an XML Bomb referring to an XML document that is valid according to the rules of an XML schema yet results in the hanging or crash of the parser or underlying server. The attack is often referred to as the Billion Laughs Attack because many proof of concept examples caused XML parsers to expand the string lol or ha up to a billion times or until server resources were exhausted.

The attack combines certain properties of XML to create valid but malicious XML using an extreme level of nested substitutions. When an XML parser attempts to expand all the nested entities it quickly exhausts all server resources.

This technique will cause the XML parsers in Cisco Unified Presence and Jabber XCP (including JabberNow appliances) to trigger high CPU and memory usage resulting in process crashes. The attack affects both client-to-server connections as well as server-to-server (federation) links.

This vulnerability is documented in the following Cisco bug IDs:

This vulnerability was assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2011-3287 for Cisco bug ID CSCtq78106 and CVE ID CVE-2011-3288 for Cisco bug IDs CSCtq89842 and CSCtq88547.

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.

CSCtq78106 - XCP Vulnerable to XML Entity Expansion Attack

Calculate the environmental score of CSCtq78106

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

CSCtq89842 - CUP Server PE Vulnerable to XML Entity Expansion Attack

Calculate the environmental score of CSCtq89842

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

CSCtq88547 - CUP Server Client Profile Agent Vulnerable to XML Entity Expansion Attack

Calculate the environmental score of CSCtq88547

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 could cause elevated memory and CPU utilization, resulting in memory exhaustion and process crashes. Repeated exploitation could result in a sustained 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.

Cisco Unified Presence Software Version

First Fixed Release

All versions prior to 8.5(4)

Upgrade to 8.5(4)

Jabber XCP Software Version, Including JabberNow Appliances

First Fixed Release

Versions prior to 4.X

These versions are vulnerable but are End of Life. No fixed software will be made available. Cisco highly recommends that customers using one of these versions migrate to a supported version.

Versions 4.X - 5.2

Migrate to 5.4.0.27581, 5.8.1.27561, or higher

Version 5.4

Upgrade to 5.4.0.27581, 5.8.1.27561, or higher

Version 5.8

Upgrade to 5.8.1.27561 or higher


Workarounds

There are no available workarounds to mitigate this vulnerability.

Obtaining Fixed Software

Cisco has released free software updates that address this vulnerability. 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

XML entity expansion attacks are well known, but Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerability against the Cisco products 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 is posted on Cisco's worldwide website at:

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

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 1.1 2012-July-18 Updated advisory metatags.
Revision 1.0 2011-September-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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