Cisco Security Advisory: Cisco IOS Software Object-group Access Control List Bypass Vulnerability

23 Sep 2009

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://www.cisco.com/warp/public/707/cisco-sa-20090923-acl.shtml

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. The
following table lists releases that correct all Cisco IOS Software
vulnerabilities that have been published on September 23, 2009, or
earlier.

http://www.cisco.com/warp/public/707/cisco-sa-20090923-bundle.shtml

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

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.

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:

  * CSCsx07114
  * CSCsu70214
  * CSCsw47076
  * CSCsv48603
  * CSCsy54122
  * CSCsu50252

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

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

CVSS Base Score - 4.3

Access Vector           - Network
Access Complexity       - Medium
Authentication          - None
Confidentiality Impact  - Parital
Integrity Impact        - None
Availability Impact     - none

CVSS Temporal Score - 3.6

Exploitability          - Functional
Remediation Level       - Official-Fix
Report Confidence       - 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    |          Availability of Repaired Releases           |
|  Release   |                                                      |
|------------+------------------------------------------------------|
|  Affected  |                                       | Recommended  |
| 12.0-Based |          First Fixed Release          |   Release    |
|  Releases  |                                       |              |
|-------------------------------------------------------------------|
| There are no affected 12.0 based releases.                        |
|-------------------------------------------------------------------|
|  Affected  |                                       | Recommended  |
| 12.1-Based |          First Fixed Release          |   Release    |
|  Releases  |                                       |              |
|-------------------------------------------------------------------|
| There are no affected 12.1 based releases.                        |
|-------------------------------------------------------------------|
|  Affected  |                                       | Recommended  |
| 12.2-Based |          First Fixed Release          |   Release    |
|  Releases  |                                       |              |
|-------------------------------------------------------------------|
| There are no affected 12.1 based releases.                        |
|-------------------------------------------------------------------|
|  Affected  |                                       | Recommended  |
| 12.3-Based |          First Fixed Release          |   Release    |
|  Releases  |                                       |              |
|-------------------------------------------------------------------|
| There are no affected 12.3 based releases.                        |
|-------------------------------------------------------------------|
|  Affected  |                                       | Recommended  |
| 12.4-Based |          First Fixed Release          |   Release    |
|  Releases  |                                       |              |
|------------+---------------------------------------+--------------|
| 12.4       | Not Vulnerable                        |              |
|------------+---------------------------------------+--------------|
|            | Vulnerable; Contact your support      |              |
| 12.4GC     | 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                        |              |
|------------+---------------------------------------+--------------|
|            |                                       | 12.4(11)MD9  |
|            |                                       |              |
| 12.4MD     | 12.4(22)MD1                           | 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                        |              |
|------------+---------------------------------------+--------------|
|            |                                       | 12.4(20)T4   |
|            | 12.4(22)T2                            |              |
|            |                                       | 12.4(22)T3   |
| 12.4T      | 12.4(20)T4                            |              |
|            |                                       | 12.4(24)T2;  |
|            | 12.4(24)T1                            | 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                        |              |
|------------+---------------------------------------+--------------|
|            |                                       | 12.4(20)T4   |
|            |                                       |              |
|            |                                       | 12.4(22)T3   |
| 12.4XZ     | Vulnerable; first fixed in 12.4T      |              |
|            |                                       | 12.4(24)T2;  |
|            |                                       | Available on |
|            |                                       | 23-OCT-2009  |
|------------+---------------------------------------+--------------|
|            |                                       | 12.4(22)T3   |
|            |                                       |              |
| 12.4YA     | Vulnerable; first fixed in 12.4T      | 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 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 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://www.cisco.com/warp/public/707/cisco-sa-20090923-acl.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 |                   | Initial |
| 1.0      | 2009-September-23 | 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.h...

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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Cisco Security Advisory: Cisco IOS Software Object-group Access Control List Bypass Vulnerability

Cisco Systems Product Security Incident Response Team