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Cisco Security Advisory: Cisco Content Services Gateway Vulnerabilities

Advisory ID: cisco-sa-20110126-csg2

http://www.cisco.com/warp/public/707/cisco-sa-20110126-csg2.shtml

Revision 1.0

For Public Release 2011 January 26 1600 UTC (GMT)

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Summary
=======

A service policy bypass vulnerability exists in the Cisco Content
Services Gateway - Second Generation (CSG2), which runs on the
Cisco Service and Application Module for IP (SAMI). Under certain
configurations this vulnerability could allow:

  * Customers to access sites that would normally match a billing
    policy to be accessed without being charged to the end customer
  * Customers to access sites that would normally be denied based on
    configured restriction policies

Additionally, Cisco IOS Software Release 12.4(24)MD1 on the Cisco
CSG2 contains two vulnerabilities that can be exploited by a remote,
unauthenticated attacker to create a denial of service condition that
prevents traffic from passing through the CSG2. These vulnerabilities
require only a single content service to be active on the Cisco CSG2 and
can be exploited via crafted TCP packets. A three-way handshake is not
required to exploit either of these vulnerabilities.

Workarounds that mitigate these vulnerabilities are not available.

This advisory is posted at
http://www.cisco.com/warp/public/707/cisco-sa-20110126-csg2.shtml.

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

The service policy bypass vulnerability affects all versions of the
Cisco IOS Software for the CSG2 prior to the first fixed release, as
indicated in the "Software Versions and Fixes" section of this advisory.

The two denial of service vulnerabilities only affect Cisco IOS Software
Release 12.4(24)MD1 on the Cisco CSG2. No other Cisco IOS Software
releases are affected.

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

To determine the version of Cisco IOS Software that is running on the
Cisco CSG2, issue the "show module" command from Cisco IOS Software on
the switch on which the Cisco CSG2 module is installed to identify what
modules and sub-modules are installed on the system.

Cisco CSG2 runs on the Cisco Service and Application Module for IP
(SAMI) card, and is identified in the following example in slot 2 via
the WS-SVC-SAMI-BB-K9 identification:

    C7600#show module
    Mod Ports Card Type                              Model              Serial No.
    --- ----- -------------------------------------- ------------------ -----------
      1    2  Supervisor Engine 720 (Active)         WS-SUP720-3BXL     JAF1226ARQS
      2    1  SAMI Module (csgk9)                    WS-SVC-SAMI-BB-K9  SAD113906P1
      4   48  CEF720 48 port 10/100/1000mb Ethernet  WS-X6748-GE-TX     SAL1127T6XY

    Mod MAC addresses                       Hw    Fw           Sw           Status
    --- ---------------------------------- ------ ------------ ------------ -------
      1  001e.be6e.a018 to 001e.be6e.a01b   5.6   8.5(2)       12.2(33)SRC5 Ok
      2  001d.45f8.f3dc to 001d.45f8.f3e3   2.1   8.7(0.22)FW1 12.4(2010040 Ok
      4  001c.587a.ef20 to 001c.587a.ef4f   2.6   12.2(14r)S5  12.2(33)SRC5 Ok

    Mod  Sub-Module                  Model              Serial       Hw     Status
    ---- --------------------------- ------------------ ----------- ------- -------
      1  Policy Feature Card 3       WS-F6K-PFC3BXL     JAF1226BNQM  1.8    Ok
      1  MSFC3 Daughterboard         WS-SUP720          JAF1226BNMC  3.1    Ok
      2  SAMI Daughterboard 1        SAMI-DC-BB         SAD114400L9  1.1    Other
      2  SAMI Daughterboard 2        SAMI-DC-BB         SAD114207FU  1.1    Other
      4  Centralized Forwarding Card WS-F6700-CFC       SAL1029VGFK  2.0    Ok

    Mod  Online Diag Status
    ---- -------------------
      1  Pass
      2  Pass
      4  Pass
    C7600#

After locating the correct slot, issue the "session slot <module number>
processor <3-9>" command to open a console connection to the respective
Cisco CSG2. Once connected to the Cisco CSG2, perform the "show version"
command:

The following example shows that the Cisco CSG2 is running software
Release 12.4(24)MD1:

    CSG2#show version
    Cisco IOS Software, SAMI Software (SAMI-CSGK9-M), Version 12.4(24)MD1, RELEASE SOFTWARE (fc2)
    Technical Support: http://www.cisco.com/techsupport
    Copyright (c) 1986-2010 by Cisco Systems, Inc.
    Compiled Wed 07-Apr-10 09:50 by prod_rel_team


    --- output truncated ---

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

The Cisco Content Services Gateway - 1st Generation (CSG) is not
affected by these vulnerabilities.

No other Cisco products are currently known to be affected by these
vulnerabilities.

Details
=======

The Cisco Content Services Gateway - Second Generation (CSG2) provides
intelligent network capabilities such as flexible policy management
and billing based on deep-packet inspection, as well as subscriber and
application awareness capabilities that enable mobile operators to
quickly and easily offer value-added, differentiated services over their
mobile data networks.

The service policy bypass vulnerability affects configurations that
allow end users to first access non-accounted or billed sites. After a
user accesses a non-accounted site, it is possible to access other sites
that are defined by a billing service policy or to access sites that may
be blocked by other policies by sending specially crafted HTTP packets.
This vulnerability only affects HTTP content traffic. HTTPS and other
traffic types are not affected.

Both denial of service vulnerabilities require only a single content
service to be active on the Cisco CSG2 and can be exploited via crafted
TCP packets. A three-way handshake is not required to exploit either of
these vulnerabilities. The vulnerabilities are triggered by TCP traffic
that transits the Cisco CSG2.

The service policy bypass vulnerability is documented in Cisco Bug ID
CSCtk35917 and has been assigned CVE ID CVE-2011-0348.

The denial of service bugs are documented in Cisco Bug ID CSCth17178 and
Cisco Bug ID CSCth41891 and have been assigned CVE IDs CVE-2011-0349 and
CVE-2011-0350 respectively.

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:

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


* CSCtk35917 ("Service Policy Bypass Vulnerability")

CVSS Base Score - 6.4
    Access Vector -            Network
    Access Complexity -        Low
    Authentication -           None
    Confidentiality Impact -   Partial
    Integrity Impact -         Partial
    Availability Impact -      None

CVSS Temporal Score - 5.3
    Exploitability -           Functional
    Remediation Level -        Official-Fix
    Report Confidence -        Confirmed

* CSCth41891/CSCth17178 ("Crafted TCP packet causes CSG2 to restart")

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 service policy bypass can allow customers
to obtain access to sites that would normally be accounted and billed
according to the billing policy without the billing policy being
engaged. Additionally, customers could gain access to URLs that are
configured in the Cisco CSG2 to be explicitly denied.

Successful exploitation of either denial of service vulnerability could
result in the Cisco CSG2 reloading or potentially hanging. Due to Cisco
Bug ID CSCtg50821, the Cisco CSG2 may not automatically recover and
may require a manual reload of the SAMI card by issuing the "hw-module
module <x> reset" CLI command from the switch.

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 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  |                                                  |
| 12.x-Based |               First Fixed Release                |
|  Releases  |                                                  |
|------------+--------------------------------------------------|
| 12.0 -     | 12.0 through 12.3 based releases are not         |
| 12.3       | affected                                         |
|------------+--------------------------------------------------|
|  Affected  |               First Fixed Release                |
| 12.4-Based |--------------------------------------------------|
|  Releases  |       DoS        |     Service Policy Bypass     |
|            | Vulnerabilities  |         Vulnerability         |
|------------+------------------+-------------------------------|
|            | All 12.4(11)MD   |                               |
|            | releases are not | All 12.4(11)MD releases are   |
|            | affected.        | affected. Migrate to a fixed  |
|            |                  | release.                      |
|            | All 12.4(15)MD   |                               |
|            | releases are not | All 12.4(15)MD releases are   |
|            | affected.        | affected. Migrate to a fixed  |
|            |                  | release.                      |
|            | All 12.4(22)MD   |                               |
| 12.4MD     | releases are not | All 12.4(22)MD releases are   |
|            | affected.        | affected. Migrate to a fixed  |
|            |                  | release.                      |
|            | Releases prior   |                               |
|            | to 12.4(24)MD1   | All 12.4(24)MD releases prior |
|            | are not          | to 12.4(24)MD3 are affected.  |
|            | affected.        |                               |
|            |                  | First fixed in 12.4(24)MD3    |
|            | First fixed in   |                               |
|            | 12.4(24)MD2      |                               |
|------------+------------------+-------------------------------|
|            |                  | All 12.4(22)MDA releases      |
|            |                  | prior to 12.4(22)MDA5 are     |
|            |                  | affected. First fixed in 12.4 |
|            | No releases      | (22)MDA5                      |
| 12.4MDA    | affected.        |                               |
|            |                  | All 12.4(24)MDA releases      |
|            |                  | prior to 12.4(24)MDA3 are     |
|            |                  | affected. First fixed in 12.4 |
|            |                  | (24)MDA3                      |
|------------+--------------------------------------------------|
|  Affected  |                                                  |
| 15.X-Based |               First Fixed Release                |
|  Releases  |                                                  |
|------------+--------------------------------------------------|
| 15.0 -     | 15.0 through 15.1 based releases are not         |
| 15.1       | affected                                         |
+---------------------------------------------------------------+

Cisco IOS Software for the CSG2 is located on Cisco Software Download
center at the following location: Cisco Interfaces and Modules --> Cisco
Services Modules --> Cisco Service Application Module for IP.


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

There are no workarounds for these vulnerabilities.


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 aware of public announcements of the service billing
bypass vulnerability on some external blog sites. However the Cisco
PSIRT is not aware of any malicious use of the vulnerabilities described
in this advisory.

These vulnerabilities were found by both internal testing and when
handling customer support calls.

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-20110126-csg2.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 1.0  | 2011-January-26  | Initial 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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