Cisco Security Advisory: Cisco IOS Software Session Initiation Protocol Denial of Service Vulnerability

23 Sep 2009

A vulnerability exists in the Session Initiation Protocol (SIP)
implementation in Cisco IOS� Software that could allow an
unauthenticated attacker to cause a denial of service (DoS) condition
on an affected device when the Cisco Unified Border Element feature
is enabled.

Cisco has released free software updates that address this
vulnerability. For devices that must run SIP there are no
workarounds; however, mitigations are available to limit exposure of
the vulnerability.

This advisory is posted at:

http://www.cisco.com/warp/public/707/cisco-sa-20090923-sip.shtml

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
earlier.

http://www.cisco.com/warp/public/707/cisco-sa-20090923-bundle.shtml

Individual publication links are in "Cisco Event Response: Semiannual
Cisco IOS Software Advisory Bundled Publication" at the following
link:

http://www.cisco.com/web/about/security/intelligence/Cisco_ERP_sep09.html

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

This vulnerability only affects devices running Cisco IOS Software
with SIP voice services enabled.

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

Cisco devices running affected Cisco IOS Software versions that are
configured to process SIP messages with the Cisco Unified Border
Element feature are affected. Cisco IOS devices that are not
configured for SIP and Cisco Unified Border Element feature are not
affected by this vulnerability.

Note: Cisco Unified Border Element feature (previously known as the
Cisco Multiservice IP-to-IP Gateway) is a special Cisco IOS Software
image that runs on Cisco multiservice gateway platforms. It provides
a network-to-network interface point for billing, security, call
admission control, quality of service, and signaling interworking.

Cisco Unified Border Element feature requires the "voice service voip" 
command and the "allow-connections" subcommand. An example of an
affected configuration is as follows:

     voice service voip
       allow-connections from-type to to-type 
    ...
    !

Recent versions of Cisco IOS Software do not process SIP messages by
default. Creating a dial peer by issuing the command "dial-peer voice"
will start the SIP processes, causing the Cisco IOS device to process
SIP messages. In addition, several features within Cisco Unified
Communications Manager Express, such as ePhones, once configured will
also automatically start the SIP process, which will cause the device
to start processing SIP messages. An example of an affected
configuration is as follows:

    dial-peer voice <Voice dial-peer tag> voip
     ...
    !

In addition to inspecting the Cisco IOS device configuration for a
dial-peer command that causes the device to process SIP messages,
administrators can also use the command show processes | include SIP
to determine whether Cisco IOS Software is running the processes that
handle SIP messages. In the following example, the presence of the
processes CCSIP_UDP_SOCKET or CCSIP_TCP_SOCKET indicates that the
Cisco IOS device is processing SIP messages:

        Router#show processes | include SIP
         149 Mwe 40F48254            4          1    400023108/24000  0 CCSIP_UDP_SOCKET
         150 Mwe 40F48034            4          1    400023388/24000  0 CCSIP_TCP_SOCKET

warning Warning: Since there are several ways a device running Cisco
IOS Software can start processing SIP messages, it is recommended
that the "show processes | include SIP" command be used to determine
whether the device is processing SIP messages instead of relying on
the presence of specific configuration commands.

To determine the Cisco IOS Software release that is running on a
Cisco product, administrators can log in to the device and issue the
show version command to display the system banner. The system banner
confirms that the device is running Cisco IOS Software by displaying
text similar to "Cisco Internetwork Operating System Software" or
"Cisco IOS Software." The image name displays in parentheses,
followed by "Version" and the Cisco IOS Software release name. Other
Cisco devices do not have the show version command or may provide
different output.

The following example identifies a Cisco product that is running
Cisco IOS Software Release 12.3(26) with an installed image name of
C2500-IS-L:

    Router#show version
    Cisco Internetwork Operating System Software
    IOS (tm) 2500 Software (C2500-IS-L), Version 12.3(26), RELEASE SOFTWARE (fc2)
    Technical Support: http://www.cisco.com/techsupport
    Copyright (c) 1986-2008 by cisco Systems, Inc.
    Compiled Mon 17-Mar-08 14:39 by dchih

    !--- output truncated

The following example identifies a Cisco product that is running
Cisco IOS Software Release 12.4(20)T with an installed image name of
C1841-ADVENTERPRISEK9-M:

    Router#show version
    Cisco IOS Software, 1841 Software (C1841-ADVENTERPRISEK9-M), Version 12.4(20)T, RELEASE SOFTWARE (fc3)
    Technical Support: http://www.cisco.com/techsupport
    Copyright (c) 1986-2008 by Cisco Systems, Inc.
    Compiled Thu 10-Jul-08 20:25 by prod_rel_team

    !--- output truncated

Additional information about Cisco IOS Software release naming
conventions is available in "White Paper: Cisco IOS Reference Guide"
at the following link:

http://www.cisco.com/warp/public/620/1.html

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

The SIP Application Layer Gateway (ALG), which is used by the Cisco
IOS NAT and firewall features of Cisco IOS Software, is not affected
by this vulnerability. Cisco IOS XE Software and Cisco IOS XR
Software are not affected by this vulnerability. No other Cisco
products are currently known to be affected by this vulnerability.

Details
=======

SIP is a popular signaling protocol that is used to manage 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 has the flexibility to accommodate other
applications that require call setup and termination. SIP call
signaling can use UDP (port 5060), TCP (port 5060), or TLS (TCP port
5061) as the underlying transport protocol.

The Cisco Unified Border Element (previously known as the Cisco
Multiservice IP-to-IP Gateway) is a special Cisco IOS Software image
that runs on Cisco multiservice gateway platforms. It provides a
network-to-network interface point for billing, security, call
admission control, quality of service, and signaling interworking.

For more information about Cisco Unified Border Element refer to the
following link:

http://www.cisco.com/en/US/products/sw/voicesw/ps5640/index.html

A DoS vulnerability exists in the SIP implementation in Cisco IOS
Software when devices are running a Cisco IOS image that contains the
Cisco Unified Border Element feature. This vulnerability is triggered
by processing a series of crafted SIP messages.

This vulnerability is documented in Cisco Bug ID CSCsx25880 and has been
assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2009-2870.

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
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

CSCsx25880 - Crafted SIP packet may cause device reload

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 vulnerability described in this
document may result in a reload of the device. The issue could be
repeatedly exploited to cause an extended 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.

Each row of the Cisco IOS Software table (below) names a Cisco IOS
release train. If a given release train is vulnerable, then the
earliest possible releases that contain the fix (along with the
anticipated date of availability for each, if applicable) are listed
in the "First Fixed Release" column of the table. The "Recommended
Release" column indicates the releases which have fixes for all the
published vulnerabilities at the time of this Advisory. A device
running a release in the given train that is earlier than the release
in a specific column (less than the First Fixed Release) is known to
be vulnerable. Cisco recommends upgrading to a release equal to or
later than the release in the "Recommended Releases" column of the
table.

+-------------------------------------------------------------------+
|   Major    |          Availability of Repaired Releases           |
|  Release   |                                                      |
|------------+------------------------------------------------------|
|  Affected  |                                       | Recommended  |
| 12.0-Based |          First Fixed Release          |   Release    |
|  Releases  |                                       |              |
|-------------------------------------------------------------------|
| There are no affected 12.0 based releases.                        |
|-------------------------------------------------------------------|
|  Affected  |                                       | Recommended  |
| 12.1-Based |          First Fixed Release          |   Release    |
|  Releases  |                                       |              |
|-------------------------------------------------------------------|
| There are no affected 12.1 based releases.                        |
|-------------------------------------------------------------------|
|  Affected  |                                       | Recommended  |
| 12.2-Based |          First Fixed Release          |   Release    |
|  Releases  |                                       |              |
|-------------------------------------------------------------------|
| There are no affected 12.2 based releases.                        |
|-------------------------------------------------------------------|
|  Affected  |                                       | Recommended  |
| 12.3-Based |          First Fixed Release          |   Release    |
|  Releases  |                                       |              |
|------------+---------------------------------------+--------------|
| 12.3       | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3B      | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3BC     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3BW     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3EU     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3JA     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3JEA    | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3JEB    | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3JEC    | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3JK     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3JL     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3JX     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3T      | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3TPC    | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3VA     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3XA     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3XB     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3XC     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3XD     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3XE     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3XF     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3XG     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3XI     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3XJ     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3XK     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3XL     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3XQ     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3XR     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3XS     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3XU     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3XW     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3XX     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3XY     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3XZ     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3YA     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3YD     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3YF     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3YG     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3YH     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3YI     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3YJ     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
|            |                                       | 12.4(15)T10  |
|            |                                       |              |
|            | Releases prior to 12.3(11)YK3 are     | 12.4(20)T4   |
|            | vulnerable, release 12.3(11)YK3 and   |              |
| 12.3YK     | later are not vulnerable; first fixed | 12.4(22)T3   |
|            | in 12.4T                              |              |
|            |                                       | 12.4(24)T2;  |
|            |                                       | Available on |
|            |                                       | 23-OCT-2009  |
|------------+---------------------------------------+--------------|
| 12.3YM     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3YQ     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
|            |                                       | 12.4(15)T10  |
|            |                                       |              |
|            | Vulnerable; first fixed in 12.4T      | 12.4(20)T4   |
|            |                                       |              |
| 12.3YS     | Releases up to and including 12.3(11) | 12.4(22)T3   |
|            | YS1 are not vulnerable.               |              |
|            |                                       | 12.4(24)T2;  |
|            |                                       | Available on |
|            |                                       | 23-OCT-2009  |
|------------+---------------------------------------+--------------|
|            |                                       | 12.4(15)T10  |
|            |                                       |              |
|            |                                       | 12.4(20)T4   |
|            |                                       |              |
| 12.3YT     | Vulnerable; first fixed in 12.4T      | 12.4(22)T3   |
|            |                                       |              |
|            |                                       | 12.4(24)T2;  |
|            |                                       | Available on |
|            |                                       | 23-OCT-2009  |
|------------+---------------------------------------+--------------|
| 12.3YU     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3YX     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3YZ     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.3ZA     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
|  Affected  |                                       | Recommended  |
| 12.4-Based |          First Fixed Release          |   Release    |
|  Releases  |                                       |              |
|------------+---------------------------------------+--------------|
| 12.4       | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.4GC     | 12.4(24)GC1                           |              |
|------------+---------------------------------------+--------------|
| 12.4JA     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.4JDA    | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.4JDC    | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.4JDD    | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.4JK     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.4JL     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.4JMA    | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.4JMB    | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.4JX     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.4MD     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.4MDA    | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.4MR     | 12.4(19)MR3                           | 12.4(19)MR3  |
|------------+---------------------------------------+--------------|
| 12.4SW     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
|            |                                       | 12.4(15)T10  |
|            | 12.4(24)T1                            |              |
|            |                                       | 12.4(20)T4   |
|            | 12.4(15)T10                           |              |
| 12.4T      |                                       | 12.4(22)T3   |
|            | 12.4(20)T3                            |              |
|            |                                       | 12.4(24)T2;  |
|            | 12.4(22)T2                            | Available on |
|            |                                       | 23-OCT-2009  |
|------------+---------------------------------------+--------------|
|            |                                       | 12.4(15)T10  |
|            |                                       |              |
|            |                                       | 12.4(20)T4   |
|            |                                       |              |
| 12.4XA     | Vulnerable; first fixed in 12.4T      | 12.4(22)T3   |
|            |                                       |              |
|            |                                       | 12.4(24)T2;  |
|            |                                       | Available on |
|            |                                       | 23-OCT-2009  |
|------------+---------------------------------------+--------------|
|            |                                       | 12.4(15)T10  |
|            |                                       |              |
|            |                                       | 12.4(20)T4   |
|            |                                       |              |
| 12.4XB     | Vulnerable; first fixed in 12.4T      | 12.4(22)T3   |
|            |                                       |              |
|            |                                       | 12.4(24)T2;  |
|            |                                       | Available on |
|            |                                       | 23-OCT-2009  |
|------------+---------------------------------------+--------------|
|            |                                       | 12.4(15)T10  |
|            |                                       |              |
|            |                                       | 12.4(20)T4   |
|            |                                       |              |
| 12.4XC     | Vulnerable; first fixed in 12.4T      | 12.4(22)T3   |
|            |                                       |              |
|            |                                       | 12.4(24)T2;  |
|            |                                       | Available on |
|            |                                       | 23-OCT-2009  |
|------------+---------------------------------------+--------------|
|            |                                       | 12.4(15)T10  |
|            |                                       |              |
|            |                                       | 12.4(20)T4   |
|            |                                       |              |
| 12.4XD     | Vulnerable; first fixed in 12.4T      | 12.4(22)T3   |
|            |                                       |              |
|            |                                       | 12.4(24)T2;  |
|            |                                       | Available on |
|            |                                       | 23-OCT-2009  |
|------------+---------------------------------------+--------------|
|            |                                       | 12.4(15)T10  |
|            |                                       |              |
|            |                                       | 12.4(20)T4   |
|            |                                       |              |
| 12.4XE     | Vulnerable; first fixed in 12.4T      | 12.4(22)T3   |
|            |                                       |              |
|            |                                       | 12.4(24)T2;  |
|            |                                       | Available on |
|            |                                       | 23-OCT-2009  |
|------------+---------------------------------------+--------------|
| 12.4XF     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.4XG     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
|            |                                       | 12.4(15)T10  |
|            |                                       |              |
|            |                                       | 12.4(20)T4   |
|            |                                       |              |
| 12.4XJ     | Vulnerable; first fixed in 12.4T      | 12.4(22)T3   |
|            |                                       |              |
|            |                                       | 12.4(24)T2;  |
|            |                                       | Available on |
|            |                                       | 23-OCT-2009  |
|------------+---------------------------------------+--------------|
| 12.4XK     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.4XL     | 12.4(15)XL5                           |              |
|------------+---------------------------------------+--------------|
|            |                                       | 12.4(15)T10  |
|            |                                       |              |
|            | Vulnerable; first fixed in 12.4T      | 12.4(20)T4   |
|            |                                       |              |
| 12.4XM     | Releases up to and including 12.4(15) | 12.4(22)T3   |
|            | XM are not vulnerable.                |              |
|            |                                       | 12.4(24)T2;  |
|            |                                       | Available on |
|            |                                       | 23-OCT-2009  |
|------------+---------------------------------------+--------------|
| 12.4XN     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
|            | Vulnerable; Contact your support      |              |
| 12.4XP     | organization per the instructions in  |              |
|            | Obtaining Fixed Software section of   |              |
|            | this advisory                         |              |
|------------+---------------------------------------+--------------|
| 12.4XQ     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.4XR     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
|            |                                       | 12.4(15)T10  |
|            |                                       |              |
|            |                                       | 12.4(20)T4   |
|            |                                       |              |
| 12.4XT     | Vulnerable; first fixed in 12.4T      | 12.4(22)T3   |
|            |                                       |              |
|            |                                       | 12.4(24)T2;  |
|            |                                       | Available on |
|            |                                       | 23-OCT-2009  |
|------------+---------------------------------------+--------------|
|            | Vulnerable; Contact your support      |              |
| 12.4XV     | organization per the instructions in  |              |
|            | Obtaining Fixed Software section of   |              |
|            | this advisory                         |              |
|------------+---------------------------------------+--------------|
|            |                                       | 12.4(15)T10  |
|            |                                       |              |
|            |                                       | 12.4(20)T4   |
|            |                                       |              |
| 12.4XW     | Vulnerable; first fixed in 12.4T      | 12.4(22)T3   |
|            |                                       |              |
|            |                                       | 12.4(24)T2;  |
|            |                                       | Available on |
|            |                                       | 23-OCT-2009  |
|------------+---------------------------------------+--------------|
|            |                                       | 12.4(15)T10  |
|            |                                       |              |
|            |                                       | 12.4(20)T4   |
|            |                                       |              |
| 12.4XY     | Vulnerable; first fixed in 12.4T      | 12.4(22)T3   |
|            |                                       |              |
|            |                                       | 12.4(24)T2;  |
|            |                                       | Available on |
|            |                                       | 23-OCT-2009  |
|------------+---------------------------------------+--------------|
|            |                                       | 12.4(15)T10  |
|            |                                       |              |
|            |                                       | 12.4(20)T4   |
|            |                                       |              |
| 12.4XZ     | Vulnerable; first fixed in 12.4T      | 12.4(22)T3   |
|            |                                       |              |
|            |                                       | 12.4(24)T2;  |
|            |                                       | Available on |
|            |                                       | 23-OCT-2009  |
|------------+---------------------------------------+--------------|
|            |                                       | 12.4(15)T10  |
|            |                                       |              |
|            |                                       | 12.4(20)T4   |
|            |                                       |              |
| 12.4YA     | Vulnerable; first fixed in 12.4T      | 12.4(22)T3   |
|            |                                       |              |
|            |                                       | 12.4(24)T2;  |
|            |                                       | Available on |
|            |                                       | 23-OCT-2009  |
|------------+---------------------------------------+--------------|
| 12.4YB     | 12.4(22)YB1                           | 12.4(22)YB4  |
|------------+---------------------------------------+--------------|
| 12.4YD     | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
| 12.4YE     | Not Vulnerable                        |              |
+-------------------------------------------------------------------+

Note: No Cisco IOS-XE or Cisco IOS Software Modularity releases are
affected by this vulnerability.

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

If the affected Cisco IOS device requires SIP for VoIP services, SIP
cannot be disabled, and therefore, no workarounds are available.
Users are advised to apply mitigation techniques to help limit
exposure to the vulnerability. Mitigation consists of allowing only
legitimate devices to connect to the routers. To increase
effectiveness, the mitigation must be coupled with anti-spoofing
measures on the network edge. This action is required because SIP can
use UDP as the transport protocol.

Additional mitigations that can be deployed on Cisco devices within
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
location:

http://www.cisco.com/warp/public/707/cisco-amb-20090923-voice.shtml

Disable SIP Listening Ports
+--------------------------

For devices that do not require SIP to be enabled, the simplest and
most effective workaround is to disable SIP processing on the device.
Some versions of Cisco IOS Software allow administrators to
accomplish this with the following commands:

    sip-ua
     no transport udp
     no transport tcp
     no transport tcp tls

Warning: When applying this workaround to devices that are
processing Media Gateway Control Protocol (MGCP) or H.323 calls, the
device will not stop SIP processing while active calls are being
processed. Under these circumstances, this workaround should be
implemented during a maintenance window when active calls can be
briefly stopped.

The "show udp connections", "show tcp brief all", and "show processes |
include SIP" commands can be used to confirm that the SIP UDP and TCP
ports are closed after applying this workaround.

Depending on the Cisco IOS Software version in use, the output of
"show ip sockets" still showed UDP port 5060 open, but sending
something to that port caused the SIP process to emit the following
message:

    *Feb  2 11:36:47.691: sip_udp_sock_process_read: SIP UDP Listener is
    DISABLED 

Control Plane Policing
+---------------------

For devices that need to offer SIP services it is possible to use
Control Plane Policing (CoPP) to block SIP traffic to the device from
untrusted sources. Cisco IOS Releases 12.0S, 12.2SX, 12.2S, 12.3T,
12.4, and 12.4T support the CoPP feature. CoPP may be configured on a
device to protect the management and control planes to minimize the
risk and effectiveness of direct infrastructure attacks by explicitly
permitting only authorized traffic sent to infrastructure devices in
accordance with existing security policies and configurations. The
following example can be adapted to the network

    !-- The 192.168.1.0/24 network and the 172.16.1.1 host are trusted.
    !-- Everything else is not trusted. The following access list is used
    !-- to determine what traffic needs to be dropped by a control plane
    !-- policy (the CoPP feature.) If the access list matches (permit)
    !-- then traffic will be dropped and if the access list does not
    !-- match (deny) then traffic will be processed by the router.

    access-list 100 deny udp 192.168.1.0 0.0.0.255 any eq 5060
    access-list 100 deny tcp 192.168.1.0 0.0.0.255 any eq 5060
    access-list 100 deny tcp 192.168.1.0 0.0.0.255 any eq 5061
    access-list 100 deny udp host 172.16.1.1 any eq 5060
    access-list 100 deny tcp host 172.16.1.1 any eq 5060
    access-list 100 deny tcp host 172.16.1.1 any eq 5061
    access-list 100 permit udp any any eq 5060
    access-list 100 permit tcp any any eq 5060
    access-list 100 permit tcp any any eq 5061

    !-- Permit (Police or Drop)/Deny (Allow) all other Layer3 and Layer4
    !-- traffic in accordance with existing security policies and
    !-- configurations for traffic that is authorized to be sent
    !-- to infrastructure devices.
    !-- Create a Class-Map for traffic to be policed by
    !-- the CoPP feature.

    class-map match-all drop-sip-class
      match access-group 100

    !-- Create a Policy-Map that will be applied to the
    !-- Control-Plane of the device.

    policy-map drop-sip-traffic
     class drop-sip-class
      drop

    !-- Apply the Policy-Map to the Control-Plane of the
    !-- device.

    control-plane
     service-policy input drop-sip-traffic

Warning: Because SIP can use UDP as a transport protocol, it
is possible to easily spoof the IP address of the sender, which may
defeat access control lists that permit communication to these ports
from trusted IP addresses.

In the above CoPP example, the access control entries (ACEs) that
match the potential exploit packets with the "permit" action result
in these packets being discarded by the policy-map "drop" function,
while packets that match the "deny" action (not shown) are not
affected by the policy-map drop function. Additional information on
the configuration and use of the CoPP feature can be found at:

http://www.cisco.com/web/about/security/intelligence/coppwp_gs.html

and

http://www.cisco.com/en/US/docs/ios/12_3t/12_3t4/feature/guide/gtrtlimt.html

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@cisco.com or security-alert@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@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 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
factual errors.

Distribution
============

This advisory is posted on Cisco's worldwide website at:

http://www.cisco.com/warp/public/707/cisco-sa-20090923-sip.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-bulletins@lists.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      | 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:

http://www.cisco.com/en/US/products/products_security_vulnerability_policy.h...

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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Cisco Security Advisory: Cisco IOS Software Session Initiation Protocol Denial of Service Vulnerability

Cisco Systems Product Security Incident Response Team