Advisory ID: cisco-sa-20090923-ios-fw

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20090923-ios-fw

Revision 1.1

For Public Release 2009 September 23 16:00  UTC (GMT)


Contents

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

Summary

Cisco IOS® devices that are configured with Cisco IOS Zone-Based Policy Firewall Session Initiation Protocol (SIP) inspection are vulnerable to denial of service (DoS) attacks when processing a specific SIP transit packet. Exploitation of the vulnerability could result in a reload of the affected device.

Cisco has released free software updates that address this vulnerability.

Workarounds that mitigate this vulnerability are available.

This advisory is posted at http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20090923-ios-fw

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.

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 affects a limited number of Cisco IOS Software releases. Consult the "Software Versions and Fixes" section of this advisory for the details of affected releases.

Only devices that are configured with Cisco IOS Zone-Based Policy Firewall SIP inspection (UDP port 5060, TCP ports 5060, and 5061) are vulnerable. Cisco IOS devices that are configured with legacy Cisco IOS Firewall Support for SIP (context-based access control (CBAC)) are not vulnerable.

Vulnerable Products

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 ©) 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 ©) 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

The device is vulnerable if the configuration has either a layer 3 or layer 7 SIP application-specific policy configured, and these policies are applied to any firewall zone. To determine whether the device is running a vulnerable configuration, log in to the device and issue the command line interface (CLI) command show policy-map type inspect zone-pair | include atch: access|protocol sip. If the output contains "Match: protocol sip", the device is vulnerable. If the output contains Match: access-group number , then the device is only vulnerable if, the referenced access list permits the SIP protocol (UDP port 5060, or TCP ports 5060 and 5061). The following example shows a vulnerable device configured with Cisco IOS Zone-Based Policy Firewall SIP inspection:

Router#show policy-map type inspect zone-pair | include atch: access|protocol sip
      Match: protocol sip
Router#

The following example shows a vulnerable device configured with SIP inspection by way of an applied access list:

Router#show policy-map type inspect zone-pair | include atch: access|protocol sip
      Match: access-group 102
Router#
Router#show access-list 102
Extended IP access list 102
    10 permit udp any any eq 5060
    20 permit tcp any any eq 5060
    30 permit tcp any any eq 5061
Router#

A device that is not configured for SIP inspection or does not support this configuration will return either a blank line or an error message. The following is an example of a device that supports Cisco IOS Firewall but does not have SIP inspection enabled:

Router#show policy-map type inspect zone-pair | include atch: access|protocol sip
Router#

Products Confirmed Not Vulnerable

No other Cisco products are currently known to be affected by this vulnerability. Products confirmed not vulnerable include:

Details

Firewalls are networking devices that control access to the network assets of an organization. Firewalls are often positioned at the entrance points into networks. Cisco IOS software provides a set of security features that enable you to configure a simple or elaborate firewall policy, according to your particular requirements.

SIP inspection in the Cisco IOS Firewall provides basic SIP inspect functionality (SIP packet inspection and pinhole opening) as well as protocol conformance and application security.

Cisco IOS Software that is configured with Cisco IOS Zone-Based Policy Firewall SIP inspection are vulnerable to a DoS attack when processing a specific SIP transit packet. Exploitation of this vulnerability will result in a reload of the affected device.

Cisco IOS Zone-Based Policy Firewall SIP inspection was first introduced in Cisco IOS Software versions 12.4(15)XZ and 12.4(20)T.

Cisco IOS Firewall CBAC support for SIP inspection by way of the ip inspect name [inspection_name] sip is not vulnerable. Additional information regarding Cisco IOS Firewall CBAC support for SIP inspection is available in the document "Firewall Support for SIP" at the following link: http://www.cisco.com/en/US/docs/ios/sec_data_plane/configuration/guide/sec_fwall_sip_supp.html

Additional information regarding Cisco IOS Zone-Based Policy Firewall SIP inspection is available in the document "Cisco IOS Firewall: SIP Enhancements: ALG and AIC" at the following link: http://www.cisco.com/en/US/docs/ios/security/configuration/guide/sec_sip_alg_aic.html

This vulnerability is documented in the following Cisco Bug ID: CSCsr18691 ( registered customers only) and has been assigned the Common Vulnerabilities and Exposures (CVE) identifier CVE-2009-2867.

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 .

CSCsr18691: Cisco IOS Software Zone-Based Policy Firewall Vulnerability

Calculate the environmental score of CSCsr18691

CVSS Base Score - 7.8

Access Vector

Access Complexity

Authentication

Confidentiality Impact

Integrity Impact

Availability Impact

Network

Low

None

None

None

Complete

CVSS Temporal Score - 6.4

Exploitability

Remediation Level

Report Confidence

Functional

Official-Fix

Confirmed

Impact

Successful exploitation of the vulnerability may result in a reload of the affected device. Repeated exploit attempts may result in a sustained DoS attack.

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 Release

Availability of Repaired Releases

Affected 12.0-Based Releases

First Fixed Release

Recommended Release

There are no affected 12.0 based releases

Affected 12.1-Based Releases

First Fixed Release

Recommended Release

There are no affected 12.1 based releases

Affected 12.2-Based Releases

First Fixed Release

Recommended Release

There are no affected 12.2 based releases

Affected 12.3-Based Releases

First Fixed Release

Recommended Release

There are no affected 12.3 based releases

Affected 12.4-Based Releases

First Fixed Release

Recommended Release

12.4

Not Vulnerable

 

12.4GC

Not Vulnerable

 

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

Not Vulnerable

 

12.4SW

Not Vulnerable

 

12.4T

Releases prior to 12.4(20)T are not vulnerable;

12.4(20)T2

12.4(22)T1

12.4(24)T

12.4(20)T4

12.4(22)T3

12.4(24)T2; Available on 23-OCT-2009

12.4XA

Not Vulnerable

 

12.4XB

Not Vulnerable

 

12.4XC

Not Vulnerable

 

12.4XD

Not Vulnerable

 

12.4XE

Not Vulnerable

 

12.4XF

Not Vulnerable

 

12.4XG

Not Vulnerable

 

12.4XJ

Not Vulnerable

 

12.4XK

Not Vulnerable

 

12.4XL

Not Vulnerable

 

12.4XM

Not Vulnerable

 

12.4XN

Not Vulnerable

 

12.4XP

Not Vulnerable

 

12.4XQ

Not Vulnerable

 

12.4XR

Not Vulnerable

 

12.4XT

Not Vulnerable

 

12.4XV

Not Vulnerable

 

12.4XW

Not Vulnerable

 

12.4XY

Not Vulnerable

 

12.4XZ

Vulnerable; first fixed in 12.4T

12.4(20)T4

12.4(22)T3

12.4(24)T2; Available on 23-OCT-2009

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)YB4

12.4(22)YB4

12.4(22)YB5; Available on 19-OCT-2009

12.4YD

Not Vulnerable

 

12.4YE

Not Vulnerable

 

Workarounds

The only workaround for this vulnerability is to disable Cisco IOS zone-based policy firewall SIP inspection in the affected device's configuration. Disabling SIP inspection will allow the rest of the firewall features to continue to function until a software upgrade can be implemented. All other firewall features will continue to perform normally. Disabling SIP Inspection will vary depending on the implementation of the SIP inspection firewall.

Obtaining Fixed Software

Cisco has released free software updates that address this vulnerability. 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.

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 by Cisco 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://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20090923-ios-fw

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.

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

2009-September-23

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.