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Cisco Security Advisory: Vulnerability in Cisco IOS Embedded Call
Processing Solutions

Revision 1.0

For Public Release 2005 January 19 1500 UTC

+----------------------------------------------------------------------

Contents
========

    Summary
    Affected Products
    Details
    Impact
    Software Versions and Fixes
    Obtaining Fixed Software
    Workarounds
    Exploitation and Public Announcements
    Status of This Notice: FINAL
    Distribution
    Revision History
    Cisco Security Procedures

+----------------------------------------------------------------------

Summary
=======

Cisco Internetwork Operating System (IOS®) Software release trains
12.1YD, 12.2T, 12.3 and 12.3T, when configured for the Cisco IOS
Telephony Service (ITS), Cisco CallManager Express (CME) or Survivable
Remote Site Telephony (SRST) may contain a vulnerability in processing
certain malformed control protocol messages.

A successful exploitation of this vulnerability may cause a reload of
the device and could be exploited repeatedly to produce a Denial of
Service (DoS). This advisory is available at
https://www.cisco.com/warp/public/707/cisco-sa-20050119-itscme.shtml

Cisco has made free software upgrades available to address this
vulnerability for all affected customers. There are workarounds
available to mitigate the effects of the vulnerability.

This vulnerability is documented by Cisco bug ID CSCee08584.

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

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

This issue affects all Cisco devices running any unfixed version of
Cisco IOS code that supports, and is configured for ITS, CME or SRST.

A Cisco device running ITS or CME will have the following line in the
configuration:

    telephony-service
    

A Cisco device running SRST will have the following line in the
configuration:

    call-manager-fallback
    

To determine the software running on a Cisco product, log in to the
device and issue the show version command to display the system banner.
Cisco IOS Software will identify itself as "Internetwork Operating
System Software" or simply "IOS." On the next line of output, the image
name will be displayed between parentheses, followed by "Version" and
the IOS release name. Other Cisco devices will not have the show
version command or will give different output.

The following example identifies a Cisco product running IOS release
12.0(3) with an installed image name of C2500-IS-L:

    Cisco Internetwork Operating System Software IOS (TM)
        
    2500 Software (C2500-IS-L), Version 12.0(3), RELEASE SOFTWARE
    

The release train label is "12.0".

The next example shows a product running IOS release 12.3(6) with an
image name of C2600-JS-MZ:

    Cisco Internetwork Operating System Software IOS (tm)
    
    C2600 Software (C2600-JS-MZ), Version 12.3(6), RELEASE SOFTWARE (fc1)
    

Additional information about Cisco IOS release naming can be found at 
https://www.cisco.com/warp/public/620/1.html.

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

ITS, CME and SRST are IOS-only features. Devices that do not run IOS
are not vulnerable.

Details
========

More information about Cisco's IOS Telephony Service (ITS) and Cisco
CallManager Express (CME) can be found here:

https://www.cisco.com/en/US/products/sw/voicesw/ps4625/index.html

More information on Cisco's Survivable Remote Site Telephony (SRST) can
be found here:

https://www.cisco.com/en/US/products/sw/voicesw/ps2169/index.html

ITS, CME and SRST are features that allow a Cisco device running IOS to
control IP Phones using the Skinny Call Control Protocol (SCCP). SCCP
is the Cisco CallManager native signaling protocol.

Certain malformed packets sent to the SCCP port on an IOS device
configured for ITS, CME or SRST may cause the target device to reload.
This issue is documented in Cisco bug ID CSCee08584.

The following commands can be used to determine if ITS or CME are
running. A device that does not have ITS or CME enabled will display:

    Router#show telephony-service
    telephony-service is not enabled
    

A device that has ITS or CME enabled will show something similar to:

    Router#show telephony-service
    CONFIG (Version=3.0)                    
    =====================                   
    Cisco CallManager Express               
    ip source-address 192.168.1.1 port 2000
    max-ephones 2                           
    max-dn 2                                
    max-conferences 8                       
    max-redirect 5                          
    time-format 12                          
    date-format mm-dd-yy                    
    keepalive 30                            
    timeout interdigit 10                   
    timeout busy 10                         
    timeout ringing 180                     
    edit DN through Web:  disabled.         
    edit TIME through web:  disabled.       
    Log (table parameters):                 
         max-size: 150                      
         retain-timer: 15                   
    create cnf-files version-stamp Jan 01 2002 00:00:00
    auto assign 1 to 2                                 
    local directory service: enabled. 
    

The following commands can be used to determine if SRST is running. A
device that does not have SRST enabled will display:

    Router#show call-manager-fallback 
    Call-manager fallback is not enabled
    

A device that has SRST enabled will show something similar to:

    Router#show call-manager-fallback 
    CONFIG
    ======
    ip source-address 192.168.1.1 port 2000
    max-ephones 2
    max-dn 4
    huntstop
    time-format 12
    date-format mm-dd-yy
    keepalive 30
    interdigit timeout 10
    busy timeout 10
    Limit number of DNs per phone:
      7910: 34
      7935: 34
      7940: 34
      7960: 34 
    

Spoofed attacks are impractical since the attacker must pass all of the
TCP/IP integrity checks first, including the initial sequence number
and source TCP port number.

Impact
======

Successful exploitation of the vulnerability may result in a device
reload. Repeated exploitation could result in a Denial of Service (DoS)
attack.

Software Versions and Fixes
===========================

Each row of the Cisco IOS software table (below) describes a release
train and the platforms or products for which it is intended. If a
given release train is vulnerable, then the earliest possible releases
that contain the fix (the "First Fixed Release") and the anticipated
date of availability for each are listed in the "Rebuild" and
"Maintenance" columns. 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. The release should be
upgraded at least to the indicated release or a later version (greater
than or equal to the First Fixed Release label).

For further information on the terms "Rebuild" and "Maintenance" please
consult the following URL:

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

When considering software upgrades, please also consult
https://www.cisco.com/en/US/products/products_security_advisories_listing.html
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") for asssistance.

+------------------------------------------+
|   Major    |  Availability of Repaired   |
|  Release   |          Releases           |
|------------+-----------------------------|
| Affected   |            |                |
| 12.1-Based | Rebuild    | Maintenance    |
| Release    |            |                |
|------------+-----------------------------|
| 12.1YD     | Migrate to 12.2(15)T13      |
|            | or later                    |
|------------+-----------------------------|
| 12.1YE     | Migrate to 12.2(15)T13      |
|            | or later                    |
|------------+-----------------------------|
| 12.1YI     | Migrate to 12.2(15)T13      |
|            | or later                    |
|------------+-----------------------------|
| Affected   |            |                |
| 12.2-Based | Rebuild    | Maintenance    |
| Release    |            |                |
|------------+-----------------------------|
| 12.2B      | Migrate to 12.3(8)T or      |
|            | later                       |
|------------+-----------------------------|
| 12.2BC     | Migrate to 12.3(9)BC or     |
|            | later                       |
|------------+-----------------------------|
| 12.2CZ     | Migrate to 12.2(15)CZ1      |
|            | or later                    |
|------------+-----------------------------|
| 12.2JK     | 12.2(15)JK2                 |
|------------+-----------------------------|
|            | 12.2(13)   |                |
|            | T14        |                |
|12.2T       |------------+----------------|
|            | 12.2(15)   |                |
|            | T13        |                |
|------------+-----------------------------|
| 12.2XB     | Migrate to 12.3(9) or       |
|            | later                       |
|------------+-----------------------------|
| 12.2XG     | Migrate to 12.2(15)T13      |
|            | or later                    |
|------------+-----------------------------|
| 12.2XM     | Migrate to 12.2(15)T13      |
|            | or later                    |
|------------+-----------------------------|
| 12.2XT     | Migrate to 12.2(15)T13      |
|            | or later                    |
|------------+-----------------------------|
| 12.2XU     | Migrate to 12.2(15)T13      |
|            | or later                    |
|------------+-----------------------------|
| 12.2XW     | Migrate to 12.2(15)T13      |
|            | or later                    |
|------------+-----------------------------|
| 12.2XZ     | Migrate to 12.2(15)T13      |
|            | or later                    |
|------------+-----------------------------|
| 12.2YA     | 12.2(4)YA8 |                |
|------------+-----------------------------|
| 12.2YB     | Migrate to 12.2(15)T13      |
|            | or later                    |
|------------+-----------------------------|
| 12.2YC     | Migrate to 12.2(15)T13      |
|            | or later                    |
|------------+-----------------------------|
| 12.2YD     | Migrate to 12.3(8)T or      |
|            | later                       |
|------------+-----------------------------|
| 12.2YF     | Migrate to 12.2(15)T13      |
|            | or later                    |
|------------+-----------------------------|
| 12.2YG     | Migrate to 12.2(15)T13      |
|            | or later                    |
|------------+-----------------------------|
| 12.2YH     | Migrate to 12.2(15)T13      |
|            | or later                    |
|------------+-----------------------------|
| 12.2YJ     | Migrate to 12.2(15)T13      |
|            | or later                    |
|------------+-----------------------------|
| 12.2YL     | Migrate to 12.3(8)T or      |
|            | later                       |
|------------+-----------------------------|
| 12.2YM     | Migrate to 12.3(8)T or      |
|            | later                       |
|------------+-----------------------------|
| 12.2YN     | Migrate to 12.3(8)T or      |
|            | later                       |
|------------+-----------------------------|
| 12.2YQ     | Migrate to 12.3(8)T or      |
|            | later                       |
|------------+-----------------------------|
| 12.2YR     | Migrate to 12.3(8)T or      |
|            | later                       |
|------------+-----------------------------|
| 12.2YS     | Migrate to 12.3(8)T or      |
|            | later                       |
|------------+-----------------------------|
| 12.2ZK     | Migrate to 12.3(8)T or      |
|            | later                       |
|------------+-----------------------------|
| 12.2ZO     | Migrate to 12.2(15)T13      |
|            | or later                    |
|------------+-----------------------------|
| 12.2ZP     | Migrate to 12.3(4)XN2 or    |
|            | later                       |
|------------+-----------------------------|
| Affected   |            |                |
| 12.3-Based | Rebuild    | Maintenance    |
| Release    |            |                |
|------------+------------+----------------|
|            | 12.3(5d)   |                |
|            |------------+----------------|
| 12.3       | 12.3(6c)   |                |
|            |------------+----------------|
|            |            | 12.3(9)        |
|------------+------------+----------------|
|            | 12.3(2)T7  |                |
|            |------------+----------------|
|            | 12.3(4)T6  |                |
|12.3T       |------------+----------------|
|            | 12.3(7)T1  |                |
|            |------------+----------------|
|            |            | 12.3(8)T       |
|------------+-----------------------------|
| 12.3XA     | Migrate to 12.3(8)T or      |
|            | later                       |
|------------+-----------------------------|
| 12.3XB     | Migrate to 12.3(8)T or      |
|            | later                       |
|------------+-----------------------------|
| 12.3XC     | Migrate to 12.3(8)T or      |
|            | later                       |
|------------+-----------------------------|
| 12.3XD     | 12.3(4)XD3 |                |
|------------+------------+----------------|
| 12.3XE     | 12.3(2)XE1 |                |
|------------+-----------------------------|
| 12.3XF     | Migrate to 12.3(11)T or     |
|            | later                       |
|------------+-----------------------------|
| 12.3XG     | 12.3(4)XG2 |                |
|------------+-----------------------------|
| 12.3XH     | Migrate to 12.3(11)T or     |
|            | later                       |
|------------+-----------------------------|
| 12.3XI     |            | 12.3(7)XI      |
|------------+------------+----------------|
| 12.3XJ     | 12.3(7)XJ2 |                |
|------------+------------+----------------|
| 12.3XK     | 12.3(4)XK1 |                |
|------------+------------+----------------|
| 12.3XL     |            | 12.3(7)XL      |
|------------+-----------------------------|
| 12.3XN     | Contact Cisco TAC           |
|------------+-----------------------------|
|            | 12.3(4)XQ1 |                |
|            | Release    |                |
| 12.3XQ     | date not   |                |
|            | yet        |                |
|            | determined |                |
+------------------------------------------+

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

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 https://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 assistance with the upgrade,
which should be free of charge.

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 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

Please 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.

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

See https://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.

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
https://www.cisco.com/public/sw-license-agreement.html, or as otherwise
set forth at Cisco.com Downloads at
https://www.cisco.com/public/sw-center/sw-usingswc.shtml.

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

The effectiveness of any workaround 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 is the most
appropriate for use in the intended network before it is deployed.

Affected devices that must run ITS, CME or SRST are vulnerable, and
there are not any specific configurations that can be used to protect
them. Applying access lists on interfaces that should not accept ITS,
CME or SRST traffic and putting firewalls in strategic locations may
greatly reduce exposure until an upgrade can be performed.

The IP Telephony Security in Depth SAFE paper at the URL below
discusses a variety of best practices that should keep your voice
network isolated from the Internet. These best practices may help to
reduce the risk of exposure, although attacks from within the local
network should always be considered a potential risk.

https://www.cisco.com/en/US/netsol/ns340/ns394/ns171/ns128/networking_solutions_white_paper09186a00801b7a50.shtml

Using 'strict-match'
+-------------------

It is possible to restrict SCCP communications to the IP specified in
the ip source-address configuration command by using the strict-match 
option. More information on this command can be found at the following
URL:

https://www.cisco.com/en/US/netsol/ns340/ns394/ns165/ns391/networking_solutions_design_guidance09186a00801f8e30.html#wp40333

Using Access Lists
+-----------------

Where possible, it is recommended to block SCCP traffic at the network
edge with an Infrastructure Access Control List (iACL) or a Transit
Access Control List (tACL).

For more information on iACLs, refer to "Protecting Your Core:
Infrastructure Protecton Access Control Lists":

https://www.cisco.com/warp/public/707/iacl.html

For more information on tACLs, refer to 'Transit Access Control Lists:
Filtering at Your Edge":

https://www.cisco.com/warp/public/707/tacl.html

Below is an example of an access list to block SCCP traffic from
anywhere but a permitted network.

Note: In SRST deployments the SCCP packets are not addressed directly
to the SRST device. The SCCP packets will be addressed to the call
control devices (typically Cisco CallManager).

In this example, the permitted telephony devices are on the
172.16.0.0/16 network and the SCCP port being used is the default, TCP
port 2000.  If the specific IP addresses of the telephony devices are
known, then the access list can be made to restrict traffic from only
those devices.

    
    !--- Permit access from any IP address in the 172.16.0.0/16 
    !--- to TCP port 2000.
    
    
    access-list 101 permit tcp 172.16.0.0 0.0.255.255 any eq 2000
    
    
    !--- Deny all traffic to port 2000.
    
    
    access-list 101 deny tcp any any eq 2000
    
    
    !--- Permit all other traffic.
    
    
    access-list 101 permit ip any any
    

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

The Control Plane Policing (CoPP) feature may be used to mitigate this
vulnerability. In the following example SCCP traffic is permitted to
and from the 192.168.10.0/24 subnet. All other TCP port 2000 traffic
destined to the device is blocked.

    access-list 140 deny   tcp 192.168.10.0 0.0.0.255 any eq 2000
    access-list 140 deny   tcp any 192.168.10.0 0.0.0.255 eq 2000
    access-list 140 permit tcp any any eq 2000
    access-list 140 deny   ip  any any
    
    class-map match-all sccp-class
      match access-group 140
    
    policy-map control-plane-policy
      class sccp-class
    
         police 8000 1500 1500 conform-action drop exceed-action drop
    
    control-plane
     service-policy input control-plane-policy
    

CoPP is available in IOS release trains 12.2S and 12.3T. Additional
information on the configuration and use of the CoPP feature can be
found at the following URL:

https://www.cisco.com/en/US/products/sw/iosswrel/ps1838/products_feature_guide09186a00801afad4.html

Exploitation and Public Announcements
=====================================

The vulnerability described by CSCee08584 was originally reported to
Cisco by SecureTest. The Cisco PSIRT is not aware of any public
announcements or malicious use of the vulnerability described in this
advisory.

Status of This Notice: FINAL
============================

THIS ADVISORY IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY
KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTY OF
MERCHANTABILITY. YOUR USE OF THE INFORMATION ON THE ADVISORY OR
MATERIALS LINKED FROM THE ADVISORY IS AT YOUR OWN RISK. CISCO RESERVES
THE RIGHT TO CHANGE OR UPDATE THIS NOTICE AT ANY TIME.

A stand-alone copy or paraphrase of the text of this security advisory
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 will be posted on Cisco's worldwide website at
https://www.cisco.com/warp/public/707/cisco-sa-20050119-itscme.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 (includes CERT/CC)
  * bugtraq@securityfocus.com
  * vulnwatch@vulnwatch.org
  * cisco@spot.colorado.edu
  * cisco-voice@puck.nether.net
  * full-disclosure@lists.netsys.com
  * 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       | 2005-Jan-19 | 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
https://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
https://www.cisco.com/go/psirt.
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