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Cisco Security Advisory: Cisco Unified Communications Manager Denial
of Service Vulnerabilities

Document ID: 98833

Advisory ID: cisco-sa-20071017-cucm

http://www.cisco.com/warp/public/707/cisco-sa-20071017-cucm.shtml

Revision 1.0

For Public Release 2007 October 17 1600 UTC (GMT)

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

Summary
=======

Cisco Unified Communications Manager (CUCM), formerly CallManager,
contains two denial of service (DoS) vulnerabilities. Large volumes
of UDP Session Initiation Protocol (SIP) INVITE messages may cause a
resource exhaustion condition on CUCM systems resulting in a kernel
panic. The CUCM Trivial File Transfer Protocol (TFTP) service
contains a buffer overflow vulnerability that may result in a denial
of service condition or allow a remote, unauthenticated user to
execute arbitrary code. There are no workarounds for these
vulnerabilities.

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

This advisory is posted at 
http://www.cisco.com/warp/public/707/cisco-sa-20071017-cucm.shtml.

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

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

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

All Cisco Unified CallManager 5.0 versions and Communications Manager
5.1 versions prior to 5.1(2) are affected by both vulnerabilities.
Cisco Unified Communications Manager version 5.1(2) is affected by
the TFTP service overflow vulnerability.

Note: Cisco Unified Communications Manager version 6.0(1) shipped
containing the fixes for these vulnerabilities.

Administrators of systems that are running CUCM versions 5.x and 6.x
can determine the software version by viewing the main page of the
CUCM Administration interface. The software version can also be
determined by running the command show version active via the command
line interface (CLI).

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

Cisco Unified CallManager versions 3.x, 4.0 and 4.1, Communications
Manager 4.2 and 4.3, and Cisco CallManager Express are not affected
by these vulnerabilities. No other Cisco products are currently known
to be affected by these vulnerabilities.

Details
=======

Cisco Unified Communications Manager (CUCM), formerly CallManager, 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.

  * SIP INVITE UDP Denial of Service:

    The CUCM Session Initiation Protocol (SIP) stack contains a DoS
    vulnerability. By flooding a CUCM system with normal SIP INVITE
    messages to UDP port 5060, it may be possible to trigger a
    resource exhaustion condition that will result in a kernel panic.
    This vulnerability is corrected in CUCM versions 5.1(2b), 5.1(3)
    and 6.0(1). This issue is documented in Cisco bug ID CSCsi75822.

  * Centralized TFTP File Locator Service Overflow:

    The CUCM TFTP service contains a buffer overflow vulnerability in
    the processing of filenames that may allow a remote,
    unauthenticated user to cause a DoS condition or execute
    arbitrary code. The TFTP service serves files via two methods:
    traditional TFTP (UDP port 69), and a HTTP server that listens on
    TCP port 6970. The HTTP server component is known as the
    Centralized TFTP File Locator Service.

    The Centralized TFTP File Locator Service allows CUCM
    administrators to store device configuration and software files
    in a central location. The Centralized TFTP File Locator Service
    becomes active when the CUCM TFTP service is enabled and an
    alternate TFTP path is configured. Please consult the following
    documentation for more information on configuring the Centralized
    TFTP File Locator Service and alternate TFTP paths:
    http://www.cisco.com/en/US/products/sw/voicesw/ps556/products_administration_guide_chapter09186a0
08037e280.html#wp1044917

    The overflow vulnerability only affects the Centralized TFTP File
    Locator Service component of the CUCM TFTP service. The
    Centralized TFTP File Locator Service is only used for
    communication between CUCM systems. The CUCM TFTP service is not
    enabled by default.

    This vulnerability is corrected in CUCM versions 5.1(2), 5.1(3)
    and 6.0(1). This issue is documented in Cisco bug ID CSCsh47712.

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

Cisco is providing 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.

Cisco will provide a base and temporal score. Customers can then
compute environmental scores to assist in determining the impact of
the vulnerability in individual networks.

CVSS is a standards based scoring method that conveys vulnerability
severity and helps determine urgency and priority of response.

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.

CSCsi75822 - CUCM SIP INVITE UDP Denial of Service 

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


CSCsh47712 - CUCM Centralized TFTP File Locator Service Overflow

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

Impact
======

Successful exploitation of these vulnerabilities may result in a DoS
condition. The TFTP service overflow vulnerability may also provide
the ability to execute arbitrary code.

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.

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

There are no workarounds for these vulnerabilities.

Filtering traffic to affected CUCM systems on screening devices can
provide a mitigation technique for both vulnerabilities:

  * Permit access to UDP port 5060 only from valid SIP devices to
    mitigate the SIP INVITE UDP DoS. Anti-spoofing measures should
    also be employed to prevent UDP spoofing.
  * Permit access to TCP port 6970 only from CUCM systems to mitigate
    the Centralized TFTP File Locator Service overflow.

There is currently no method to configure filtering directly on a
CUCM system.

Filters that deny SIP packets using UDP port 5060 and HTTP packets on
TCP port 6970 should be deployed throughout the network as part of a
transit access control list (tACL) policy for protection of traffic
that enters the network at ingress access points. Filters for SIP
packets using UDP port 5060 and HTTP packets on TCP port 6970 should
be deployed in front of vulnerable network devices so that traffic is
allowed from trusted clients only.

Additional information about tACLs is available in Transit Access
Control Lists: Filtering at Your Edge:

http://www.cisco.com/en/US/tech/tk648/tk361/technologies_white_paper09186a00801afc76.shtml

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

http://www.cisco.com/warp/public/707/cisco-air-20071017-cucm.shtml

Obtaining Fixed Software
========================

Cisco will make free software available to address this vulnerability
for affected customers. This advisory will be updated as fixed
software becomes available. 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/public/sw-license-agreement.html , or as 
otherwise set forth at Cisco.com Downloads at 
http://www.cisco.com/public/sw-center/sw-usingswc.shtml.

Do not contact either "psirt@cisco.com" or "security-alert@cisco.com"
for software upgrades.

Fixed software for CUCM can be obtained here:

http://www.cisco.com/pcgi-bin/tablebuild.pl/callmgr-51?psrtdcat20e2 

The vulnerabilities contained in this advisory were first fixed in
CUCM versions 5.1(2) and 5.1(2b) respectively. Customers who are not
using the SIP protocol for voice communications can opt to upgrade to
CUCM version 5.1(2) to obtain the fix for the TFTP vulnerability;
however, Cisco recommends upgrading to the latest CUCM code to take
advantage of fixed software. Customers using SIP are encouraged to
upgrade to CUCM version 5.1(2b) or later.

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 agreement 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 who do not hold a Cisco
service contract and customers who purchase through third-party
vendors but are unsuccessful at obtaining fixed software through
their point of sale should get their 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

Have your product serial number available and give the URL of this
notice as evidence of your entitlement to a free upgrade. Free
upgrades for non-contract customers must be requested through the
TAC.

Refer to http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml
for additional TAC contact information, including special 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.

These vulnerabilities were discovered internally 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-20071017-cucm.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@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 |             | Initial      |
| 1.0      | 2007-Oct-17 | 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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