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Cisco Security Advisory

Cisco Content Services Gateway Vulnerabilities

Advisory ID: cisco-sa-20110126-csg2

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20110126-csg2

Revision 1.0

For Public Release 2011 January 26 16:00  UTC (GMT)


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://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20110126-csg2.

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 ( registered customers only) and has been assigned CVE ID CVE-2011-0348.

The denial of service bugs are documented in Cisco Bug ID CSCth17178 ( registered customers only) and Cisco Bug ID CSCth41891 ( registered customers only) 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

Calculate the environmental score of CSCtk35917

CVSS Base Score - 6.4

Access Vector

Access Complexity

Authentication

Confidentiality Impact

Integrity Impact

Availability Impact

Network

Low

None

Partial

Partial

None

CVSS Temporal Score - 5.3

Exploitability

Remediation Level

Report Confidence

Functional

Official-Fix

Confirmed

CSCth41891/CSCth17178: Crafted TCP packet causes CSG2 to restart

Calculate the environmental score of CSCth41891/CSCth17178

CVSS Base Score - 7.8

Access Vector

Access Complexity

Authentication

Confidentiality Impact

Integrity Impact

Availability Impact

 

Low

None

None

None

Complete

CVSS Temporal Score - 6.4

Exploitability

Remediation Level

Report Confidence

Functional

Official-Fix

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 ( registered customers only) , 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 Release

Availability of Repaired Releases

Affected 12.x-Based Releases

First Fixed Release

12.0 - 12.3

12.0 through 12.3 based releases are not affected

Affected 12.4-Based Releases

First Fixed Release

DoS Vulnerabilities

Service Policy Bypass Vulnerability

12.4MD

All 12.4(11)MD releases are not affected.

All 12.4(15)MD releases are not affected.

All 12.4(22)MD releases are not affected.

Releases prior to 12.4(24)MD1 are not affected.

First fixed in 12.4(24)MD2

All 12.4(11)MD releases are affected. Migrate to a fixed release.

All 12.4(15)MD releases are affected. Migrate to a fixed release.

All 12.4(22)MD releases are affected. Migrate to a fixed release.

All 12.4(24)MD releases prior to 12.4(24)MD3 are affected.

First fixed in 12.4(24)MD3

12.4MDA

No releases affected.

All 12.4(22)MDA releases prior to 12.4(22)MDA5 are affected. First fixed in 12.4(22)MDA5

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 Releases

First Fixed Release

15.0 - 15.1

15.0 through 15.1 based releases are not 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://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20110126-csg2

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/web/about/security/psirt/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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