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Cisco Security Advisory

Cisco IOS Software Object-group Access Control List Bypass Vulnerability

Advisory ID: cisco-sa-20090923-acl

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

Revision 1.1

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


Summary

A vulnerability exists in Cisco IOS® software where an unauthenticated attacker could bypass access control policies when the Object Groups for Access Control Lists (ACLs) feature is used. Cisco has released free software updates that address this vulnerability. There are no workarounds for this vulnerability other than disabling the Object Groups for ACLs feature.

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

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

Vulnerable Products

Any Cisco device configured with ACLs using the object group feature and running an affected Cisco IOS software version is affected by this vulnerability.

Note: The Object Groups for ACLs feature was introduced in Cisco IOS software version 12.4(20)T.

To verify whether object groups are configured in a Cisco IOS device, use the show object-group command in user EXEC or privileged EXEC mode. The following example displays a sample output from the show object-group command when object groups are configured:

Router# show object-group
Network object group my_host_group
 host 172.18.104.123

Service object group my_allowed_services
 tcp eq www
 tcp eq 443

Alternatively, administrators can also use the show running config | include ^ (permit|deny) .*object-group command to verify whether object groups are configured, as shown in the following example:

Router#show running-config | include ^ (permit|deny) .*object-group
 permit object-group my_allowed_services host 10.10.1.1 host 10.20.1.1
 permit tcp any object-group my_host_group eq 22

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

Products Confirmed Not Vulnerable

Note: The Cisco Catalyst 6500 Object Groups feature for policy-based ACLs (PBACLs) is not affected by this vulnerability.

Cisco devices that are not configured with object groups are not vulnerable.

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

In Cisco IOS Software an object group can contain a single object (such as a single IP address, network, or subnet) or multiple objects (such as a combination of multiple IP addresses, networks, or subnets). In an ACL that is based on an object group, administrators can create a single access control entry (ACE) that uses an object group name instead of creating many ACEs, which each would require a different IP address. A similar object group, such as a protocol port group, can be extended to limit access to a set of applications for a user group to a server group.

Note: The Cisco Catalyst 6500 Object Groups feature for policy-based ACLs (PBACLs) is not affected by this vulnerability.

A vulnerability exists in Cisco IOS Software that could allow an unauthenticated attacker to bypass access control policies when the Object Groups for ACLs feature is used.

Note: The Object Groups for ACLs feature was introduced in Cisco IOS software version 12.4(20)T.

This vulnerability is documented in the following Cisco Bug IDs:

This vulnerability has been assigned Common Vulnerabilities and Exposures (CVE) identifier CVE-2009-2862.

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 .

Object-group Access Control List Bypass CSCsx07114, CSCsu70214, CSCsw47076, CSCsv48603, CSCsy54122, CSCsu50252

Calculate the environmental score of CSCsx07114, CSCsu70214, CSCsw47076, CSCsv48603, CSCsy54122, CSCsu50252

CVSS Base Score - 4.3

Access Vector

Access Complexity

Authentication

Confidentiality Impact

Integrity Impact

Availability Impact

Network

Medium

None

Partial

None

None

CVSS Temporal Score - 3.6

Exploitability

Remediation Level

Report Confidence

Functional

Official-Fix

Confirmed

Impact

Successful exploitation of the vulnerability may allow an attacker to access resources that should be protected by the Cisco IOS device.

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

Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory

 

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

12.4(22)MD1

12.4(11)MD9

12.4(15)MD3

12.4(22)MD1

12.4MDA

12.4(22)MDA1

12.4(22)MDA1

12.4MR

Not Vulnerable

 

12.4SW

Not Vulnerable

 

12.4T

12.4(22)T2

12.4(20)T4

12.4(24)T1

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

12.4YD

12.4(22)YD1

12.4(22)YD1

12.4YE

12.4(22)YE1

12.4(22)YE1

12.4YG

Not Vulnerable

 

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


Workarounds

There are no workarounds for this vulnerability other than disabling the Object Groups for ACLs feature.

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.

  • +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 found 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://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20090923-acl

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

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.


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