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Cisco Security Advisory: Cisco Unified Communications Manager Session Initiation Protocol Denial of Service Vulnerability
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Cisco Security Advisory: Cisco Unified Communications Manager Session
Initiation Protocol Denial of Service Vulnerability
Advisory ID: cisco-sa-20090923-cm
For Public Release 2009 September 23
Cisco Unified Communications Manager, which was formerly Cisco
Unified CallManager, contains a denial of service (DoS) vulnerability
in the Session Initiation Protocol (SIP) service. An exploit of this
vulnerability may cause an interruption in voice services.
Cisco has released free software updates that address this
vulnerability. There are no workarounds for this vulnerability.
This advisory is posted at:
Note: Cisco IOS® Software is also affected by the vulnerability
described in this advisory. A companion advisory for Cisco IOS
software is available at:
Note: The September 23, 2009, Cisco IOS Security Advisory bundled
publication includes eleven Security Advisories. Ten of the
advisories address vulnerabilities in Cisco IOS Software, and one
advisory addresses a vulnerability in Cisco Unified Communications
Manager. Each advisory lists the releases that correct the
vulnerability or vulnerabilities detailed in the advisory. The
following table lists releases that correct all Cisco IOS Software
vulnerabilities that have been published on September 23, 2009, or
Individual publication links are in "Cisco Event Response: Semiannual
Cisco IOS Software Advisory Bundled Publication" at the following
The vulnerability described in this document applies to the Cisco
Unified Communications Manager.
The following Cisco Unified Communications Manager versions are
* Cisco Unified Communications Manager 5.x versions prior to 5.1(3g)
* Cisco Unified Communications Manager 6.x versions prior to 6.1(4)
* Cisco Unified Communications Manager 7.0.x versions prior to 7.0(2a)su1
* Cisco Unified Communications Manager 7.1.x versions prior to 7.1(2)
Cisco Unified CallManager versions 4.x are not affected by this
vulnerability. Administrators of systems that are running Cisco
Unified Communications Manager versions 5.x, 6.x and 7.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.
A SIP trunk must be configured for the Cisco Unified CallManager
server to begin listening for SIP messages on TCP and UDP port 5060
and TCP/5061. However, in Cisco Unified Communications Manager
versions 5.x and later, the use of SIP as a call signaling protocol
is enabled by default and cannot be disabled.
Cisco IOS Software is also affected by this vulnerability, but it is
associated with different Cisco bug IDs. A companion security
advisory for Cisco IOS Software is available at:
Products Confirmed Not Vulnerable
Cisco Unified CallManager versions 4.x are not affected by this
vulnerability. With the exception of Cisco IOS software, no other
Cisco products are currently known to be affected by this
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, voice-over-IP gateways, and
SIP is a popular signaling protocol that manages voice and video
calls across IP networks such as the Internet. SIP is responsible for
handling all aspects of call setup and termination. Voice and video
are the most popular types of sessions that SIP handles, but the
protocol is flexible enough to accommodate other applications that
require call setup and termination. SIP call signaling can use UDP
(port 5060), TCP (port 5060), or Transport Layer Security (TLS; TCP
port 5061) as the underlying transport protocol.
A DoS vulnerability exists in the SIP implementation of the Cisco
Unified Communications Manager. This vulnerability could be triggered
when Cisco Unified Communications Manager processes crafted SIP
messages. An exploit could lead to a reload of the main Cisco Unified
Communications Manager process.
This vulnerability is documented in Cisco bug ID CSCsz95423 and has been
assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2009-2864.
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
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
Cisco has also provided a CVSS calculator to help compute the
environmental impact for individual networks at:
CSCsz95423 - Crafted SIP packet may cause CM process to crash
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
Successful exploitation of the vulnerability that is described in
this advisory could result in a reload of the Cisco Unified
Communications Manager process, which may result in the interruption
of voice services.
Software Versions and Fixes
When considering software upgrades, also consult:
and any subsequent advisories to determine exposure and a complete
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.
The following table contains the first fixed software release for
this vulnerability. A device running a version of the given release
in a specific row (less than the First Fixed Release) is known to be
| Release | First Fixed Version |
| 4.x | Not Vulnerable |
| 5.x | 5.1(3g) |
| 6.x | 6.1(4) |
| 7.0.x | 7.0(2a)su1 |
| 7.1.x | 7.1(2) |
There are no workarounds for this vulnerability.
It is possible to mitigate this vulnerability by implementing
filtering on screening devices and permitting TCP/UDP access to ports
5060 and TCP/5061 only from networks that require SIP access to Cisco
Unified Communications Manager servers.
If Cisco Unified Communications Manager does not need to provide SIP
services, administrators can configure the Cisco Unified
Communications Manager to listen for SIP messages on non standard
ports. Use the following instructions to change the ports from their
Step 1 Log into the Cisco Unified CallManager Administration web
Step 2 Navigate to System > Cisco Unified CM and locate the
appropriate Cisco Unified Communications Manager.
Step 3 Change the fields SIP Phone Port and SIP Phone Secure Port
fields to a non standard port and click Save.
SIP Phone Port, which is 5060 by default, refers to the TCP and UDP
ports where the Cisco Unified Communications Manager listens for
normal SIP messages, and SIP Phone Secure Port, by default 5061,
refers to the TCP port where the Cisco Unified Communications Manager
listens for SIP over TLS messages. For additional information about
this procedure, refer to the "Updating a Cisco Unified Communications
Manager" section of the "Cisco Unified Communications Manager
Administration Guide" at:
Note: For a SIP port 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:
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
Denial of Service Vulnerabilities in Cisco Unified Communications
Manager and Cisco IOS Software", which is available at the following
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:
or as otherwise set forth at Cisco.com Downloads at:
Do not contact psirt@xxxxxxxxx or security-alert@xxxxxxxxx for
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
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@xxxxxxxxx
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.
for additional TAC contact information, including localized telephone
numbers, and instructions and e-mail addresses for use in various
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 discovered during 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
This advisory is posted on Cisco's worldwide website at:
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.
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 | | Initial |
| 1.0 | 2009-September-23 | 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:
This includes instructions for press inquiries regarding Cisco security
notices. All Cisco security advisories are available at:
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