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

Type securityvulns
Reporter Securityvulns
Modified 2008-01-17T00:00:00



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) SR3
  • Cisco Unified Communications Manager 4.3 Versions prior to 4.3(1) SR1

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 interface.

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 CSCsj22605.

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

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 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 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 -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.8 (Darwin)

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