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Category:   Application (VoIP)  >   Cisco Unified Communications Manager (CallManager) Vendors:   Cisco
Cisco Unified Communications Manager Buffer Overflow in Certificate Trust List Provider Service Lets Remote Users Execute Arbitrary Code
SecurityTracker Alert ID:  1019223
SecurityTracker URL:
CVE Reference:   CVE-2008-0027   (Links to External Site)
Date:  Jan 16 2008
Impact:   Execution of arbitrary code via network, User access via network
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): 4.0, 4.1 prior to 4.1(3) SR5c, 4.2 prior to 4.2(3) SR3, and 4.3 prior to 4.3(1) SR1
Description:   A vulnerability was reported in Cisco Unified Communications Manager. A remote user can execute arbitrary code on the target system.

A remote user can send specially crafted data to trigger a heap overflow in the Certificate Trust List Provider service on TCP port 2444 and execute arbitrary code on the target system.

Versions 3.3, 5.0, 5.1, 6.0, and 6.1 are not affected. Cisco CallManager Express is not affected.

Cisco has assigned Cisco Bug ID CSCsj22605 to this vulnerability.

TippingPoint reported this vulnerability.

Impact:   A remote user can execute arbitrary code on the target system.
Solution:   Cisco has released fixed versions: 4.1(3) SR5c, 4.2(3) SR3, 4.3(1) SR1.

The Cisco advisory is available at:

Vendor URL: (Links to External Site)
Cause:   Boundary error

Message History:   None.

 Source Message Contents

Subject:  Cisco Security Advisory: Cisco Unified Communications Manager CTL

Hash: SHA1

Cisco Security Advisory: Cisco Unified Communications Manager CTL
Provider Heap Overflow

Document ID: 100345

Advisory ID: cisco-sa-20080116-cucmctl

Revision 1.0

For Public Release 2008 January 16 1600 UTC (GMT)

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


Cisco Unified Communications Manager (CUCM), formerly CallManager,
contains a heap overflow vulnerability in the Certificate Trust List
(CTL) Provider service that could allow a remote, unauthenticated
user to cause a denial of service (DoS) condition or execute
arbitrary code. There is a workaround for this vulnerability.

Cisco has made free software available to address these
vulnerabilities for affected customers.

Common Vulnerabilities and Exposures (CVE) identifier CVE-2008-0027
has been assigned to this vulnerability.

This advisory is posted at

Affected Products

Note: Cisco Unified CallManager Versions 4.2, 4.3, 5.1 and 6.0 have
been renamed as Cisco Unified Communications Manager. CUCM Versions
3.3, 4.0, 4.1 and 5.0 retain the Cisco Unified CallManager name.

Vulnerable Products

These products are vulnerable:

  * Cisco Unified CallManager 4.0
  * Cisco Unified CallManager 4.1 Versions prior to 4.1(3)SR5c
  * Cisco Unified Communications Manager 4.2 Versions prior to 4.2(3)
  * Cisco Unified Communications Manager 4.3 Versions prior to 4.3(1)

The version of software running on a CUCM 4.x system can be
determined by navigating to Help > About Cisco Unified CallManager
and selecting the Details button via the CUCM Administration

Products Confirmed Not Vulnerable

CUCM Versions 3.3, 5.0, 5.1, 6.0, 6.1 and Cisco CallManager Express
are not affected by this vulnerability. No other Cisco products are
currently known to be affected by this vulnerability.


Cisco Unified Communications Manager (CUCM) 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 (VoIP)
gateways, and multimedia applications.

When a CUCM server is deployed in secure mode, a Certificate Trust
List (CTL) is used by Cisco Unified IP Phone devices to verify the
identity of CUCM servers. The CTL contains public keys and other
information to allow the Cisco IP Phone devices to establish a
trusted relationship with a CUCM server. The CTL is provisioned using
the CTL Provider service on a CUCM server and with the CTL Provider
client on an administrator workstation. The CTL Provider service
needs to be enabled during the initial configuration of a CUCM server
/cluster or when changes are required to the CTL. Please consult the
Workarounds section of this advisory for information on how to
determine if the CTL Provider service is enabled on a CUCM server.

The CTL Provider service of the CUCM contains a heap overflow
vulnerability that could allow a remote, unauthenticated user to
cause a DoS condition or execute arbitrary code. The CTL Provider
service listens on TCP port 2444 by default, but the port can be
modified by the user. This issue is documented in Cisco Bug ID

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

Cisco has also provided a CVSS calculator to help compute the
environmental impact for individual networks at 

CSCsj22605 - CUCM CTL Provider Heap Overflow Vulnerability

CVSS Base Score - 10 

    Access Vector -            Network
    Access Complexity -        Low
    Authentication -           None
    Confidentiality Impact -   Complete
    Integrity Impact -         Complete
    Availability Impact -      Complete

CVSS Temporal Score - 8.3 

    Exploitability -           Functional
    Remediation Level -        Official-Fix
    Report Confidence -        Confirmed


Successful exploitation of this vulnerability may result in a DoS
condition or the execution of arbitrary code.

Software Versions and Fixes

When considering software upgrades, also consult 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.


It is possible to workaround the vulnerability by disabling the CTL
Provider service when not in use. Access to the CTL Provider service
is required for the initial configuration of the CUCM authentication
and encryption features, or during configuration updates. For the
CUCM 4.x systems, please consult the following documentation for
details on how to disable the CUCM services:

Filtering traffic to the affected CUCM systems on screening devices
can be used as a mitigation technique for this vulnerability. To
mitigate the CTL Producer service overflow, access to TCP port 2444
should be permitted only between the CUCM servers and administrator
workstations running the CTL Provider client. There is currently no
supported method to configure filtering directly on a CUCM system.

It is possible to change the default ports of the CTL Provider (TCP
port 2444) service. If changed, filtering should be based on the port
value used. The value of the port can be viewed in CUCM
Administration interface by following the System > Service Parameters
menu and selecting the CTL Provider service.

Filters blocking access to TCP port 2444 should be deployed at the
network edge as part of a transit access control list (tACL). Further
information about transit access control lists is available in the
white paper "Transit Access Control Lists: Filtering at Your Edge,"
which is available at the following link:

Additional mitigations that can be deployed on Cisco devices within
the network are available in the Cisco Applied Mitigation Bulletin
companion document for this advisory:

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 Downloads at 

Do not contact or for
software upgrades.

Fixed software for CUCM can be obtained here:

|  CUCM   |  Fixed  | Recommended |   Download    |
| Version | Release |   Release   |   Location    |
|         |         | Upgrade to  |               |
| CUCM    |         | a fixed     |               |
| 4.0     | N/A     | Version of  | N/A           |
|         |         | CUCM 4.1 or |               |
|         |         | later       |               |
|         |         |             | http://       |
|         | CUCM    | CUCM 4.1(3) | |
| CUCM    | 4.1(3)  | SR6 or      | /pcgi-bin/    |
| 4.1     | SR5c    | later       | |
|         |         |             | /callmgr-41?  |
|         |         |             | psrtdcat20e2  |
|         |         |             | http://       |
|         | CUCM    | CUCM 4.2(3) | |
| CUCM    | 4.2(3)  | SR3 or      | /pcgi-bin/    |
| 4.2     | SR3     | later       | |
|         |         |             | /callmgr-42?  |
|         |         |             | psrtdcat20e2  |
|         |         |             | http://       |
|         | CUCM    | CUCM 4.3(1) | |
| CUCM    | 4.3(1)  | SR1a or     | /pcgi-bin/    |
| 4.3     | SR1     | later       | |
|         |         |             | /callmgr-43?  |
|         |         |             | psrtdcat20e2  |

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

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:

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
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 reported to Cisco by TippingPoint. Cisco would
like to thank TippingPoint for reporting this vulnerability and
working with us towards resolution of this problem.

Status of This Notice: FINAL


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.


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 History

| Revision |                 | Initial  |
| 1.0      | 2008-January-16 | 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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