Cisco Security Advisory: Cisco Unified Communications Manager Session Initiation Protocol Denial of Service Vulnerabilities

Cisco Systems Product Security Incident Response Team psirt at cisco.com
Wed Sep 22 11:00:00 CDT 2010


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Cisco Unified Communications Manager Session Initiation Protocol
Denial of Service Vulnerabilities

Advisory ID: cisco-sa-20100922-cucmsip

http://www.cisco.com/warp/public/707/cisco-sa-20100922-cucmsip.shtml

Revision 1.0

For Public Release 2010 September 22 1600 UTC (GMT)

- ---------------------------------------------------------------------

Summary
=======

Cisco Unified Communications Manager contains two denial of service
(DoS) vulnerabilities that affect the processing of Session
Initiation Protocol (SIP) messages. Exploitation of these
vulnerabilities could cause an interruption of voice services.

To address these vulnerabilities, Cisco has released free software
updates. There is a workaround for these vulnerabilities.

This advisory is posted at 
http://www.cisco.com/warp/public/707/cisco-sa-20100922-cucmsip.shtml

Note: Cisco IOS Software is also affected by the vulnerabilities
described in this advisory. A companion advisory for Cisco IOS
software is available at:

http://www.cisco.com/warp/public/707/cisco-sa-20100922-sip.shtml

Note: The September 22, 2010, Cisco IOS Software Security Advisory
bundled publication includes six Cisco Security Advisories. Five of
the advisories address vulnerabilities in Cisco IOS Software and one
advisory addresses vulnerabilities in Cisco Unified Communications
Manager. Each advisory lists the releases that correct the
vulnerability or vulnerabilities detailed in the advisory. The table
at the following URL lists releases that correct all Cisco IOS
Software vulnerabilities that have been published on September 22,
2010, or earlier:

http://www.cisco.com/warp/public/707/cisco-sa-20100922-bundle.shtml

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_sep10.html

Affected Products
=================

Vulnerable Products
+------------------

The following products are affected by the vulnerabilities that are
described in this advisory:

  * Cisco Unified Communications Manager 6.x
  * Cisco Unified Communications Manager 7.x
  * Cisco Unified Communications Manager 8.x

Administrators of systems that are running Cisco Unified
Communications Manager versions 6.x, 7.x and 8.x can determine the
software version by viewing the main page of the Cisco Unified
Communications Manager Administration interface. The software version
can also be determined by running the show version active command via
the command-line interface.

Products Confirmed Not Vulnerable
+--------------------------------

Cisco Unified Communications Manager version 4.x is not affected by
these vulnerabilities. No other Cisco products are currently known to
be affected by these vulnerabilities.

Details
=======

Cisco Unified Communications Manager is the call processing component
of the Cisco IP Telephony solution that extends enterprise telephony
features and functions to packet telephony network devices such as IP
phones, media processing devices, VoIP gateways, and multimedia
applications.

Cisco Unified Communications Manager contains two DoS vulnerabilities
that involve the processing of SIP messages. Each vulnerability is
triggered by a malformed SIP message that could cause a critical
process to fail, which could result in the disruption of voice
services. All SIP ports (TCP ports 5060 and 5061 and UDP ports 5060
and 5061) are affected.

The first SIP DoS vulnerability is documented in Cisco Bug ID
CSCta31358 ( registered customers only) and has been assigned the CVE
identifier CVE-2010-2835. This vulnerability is fixed in Cisco
Unified Communications Manager versions 6.1(5), 7.0(2a)su3, 7.1(3b)
su2, 7.1(5) and 8.0(1). The corresponding IOS defect is CSCta20040.

The second SIP DoS vulnerability is documented in Cisco Bug ID
CSCtf14987 ( registered customers only) and has been assigned the CVE
identifier CVE-2010-2834. The second vulnerability is fixed in Cisco
Unified Communications Manager versions 6.1(5)SU1, 7.1(5) and 8.0(2).
The corresponding IOS defect is CSCtf72678.

Vulnerability Scoring Details
=============================

Cisco has provided scores for the vulnerabilities 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

CSCta31358 - c3945 GW crashes while testing REFER method with invalid
             Refer-To header

CVSS Base Score - 7.8
Access Vector           Network
Access Complexity       Low
Authentication          None
Confidentiality Impact  None
Integrity Impact        None
Availability Impact     Complete

CVSS Temporal Score - 6.4
Exploitability          Functional
Remediation Level       Official Fix
Report Confidence       Confirmed

CSCtf14987 - CCM Coredump Generated During UDP SIP Registration Fuzzing 

CVSS Base Score - 7.8
Access Vector           Network
Access Complexity       Low
Authentication          None
Confidentiality Impact  None
Integrity Impact        None
Availability Impact     Complete

CVSS Temporal Score - 6.4
Exploitability          Functional
Remediation Level       Official Fix
Report Confidence       Confirmed

Impact
======

Successful exploitation of the vulnerabilities that are described in
this advisory could result in the interruption of voice services.
Cisco Unified Communications Manager will restart the affected
processes, but repeated attacks may 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      | Recommended |
|  Communication Manager  |   Release   |
|         Version         |             |
|-------------------------+-------------|
| 6.x                     | 6.1(5)SU1   |
|-------------------------+-------------|
| 7.x                     | 7.1(5b)SU2  |
|-------------------------+-------------|
| 8.x                     | 8.0(3a)     |
+---------------------------------------+

Note: The recommended releases listed in the table above are the
latest Cisco Unified Communications Manager versions available at the
publication of this advisory, and each release includes software
fixes for all the vulnerabilities described in this advisory.

Cisco Unified Communications Manager software can be downloaded at
the following link:

http://tools.cisco.com/support/downloads/go/Redirect.x?mdfid=268439621

Workarounds
===========

For customers who do not use SIP in their environment, there is a
workaround for these vulnerabilities. Cisco Unified Communication
Manager versions 6.1(4), 7.1(2) and 8.0(1) introduced the ability to
disable SIP processing. SIP processing is enabled by default. Use the
following instructions to disable SIP processing:

Step 1: Log into the Cisco Unified CM Administration web interface.

Step 2: Navigate to System > Service Parameters and select the
appropriate Cisco Unified Communications Manager server and the
"Cisco CallManager" service.

Step 3: Change the "SIP Interoperability Enabled" parameter to False,
and click Save.

Note: For a SIP processing change to take effect, the Cisco
CallManager Service must be restarted. For information on how to
restart the service, refer to the "Restarting the Cisco CallManager
Service" section of the document at:

http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/admin/7_1_2/ccmcfg/b03dpi.html#wp1075124

It is possible to mitigate these vulnerabilities by implementing
filtering on screening devices and permitting access to TCP ports
5060 and 5061 and UDP ports 5060 and 5061 only from networks that
require SIP access to Cisco Unified Communications Manager servers.

Additional mitigations that can be deployed on Cisco devices in the
network are available in the companion document "Cisco Applied
Mitigation Bulletin: Identifying and Mitigating Exploitation of the
Multiple Vulnerabilities in Cisco Voice Products", which is available
at the following location:

http://www.cisco.com/warp/public/707/cisco-amb-20100922-voice.shtml

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 at cisco.com or security-alert at 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 at 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 vulnerabilities described in this advisory.

All vulnerabilities described in this advisory were discovered as a
result of internal testing conducted by Cisco.

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://www.cisco.com/warp/public/707/cisco-sa-20100922-cucmsip.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 at cisco.com
  * first-bulletins at lists.first.org
  * bugtraq at securityfocus.com
  * vulnwatch at vulnwatch.org
  * cisco at spot.colorado.edu
  * cisco-nsp at puck.nether.net
  * full-disclosure at lists.grok.org.uk
  * comp.dcom.sys.cisco at 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 |                   | Initial |
| 1.0      | 2010-September-22 | 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/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
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