Advisory ID: cisco-sa-20110330-acs
For Public Release 2011 March 30 16:00 UTC (GMT)
A vulnerability exists in some Cisco Secure Access Control System (ACS) versions that could allow a remote, unauthenticated attacker to change the password of any user account to any value without providing the account's previous password. Successful exploitation requires the user account to be defined on the internal identity store.
This vulnerability does not allow an attacker to perform any other changes to the ACS database. That is, an attacker cannot change access policies, device properties, or any account attributes except the user password.
Cisco has released free software updates that address this vulnerability. There is no workaround for this vulnerability.
This advisory is posted at http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20110330-acs.
The following Cisco Secure ACS versions are affected by this vulnerability:
- Cisco Secure ACS version 5.1 with patch 3, 4, or 5 (or any combination of these patches) installed and without patch 6 or later installed
- Cisco Secure ACS version 5.2 without any patches installed
- Cisco Secure ACS version 5.2 with patch 1 or 2 (or both of these patches) installed and without patch 3 or later installed
The previous list applies to both the hardware appliance and the software-only versions of the product.
The following methods can be used to determine which version of the Cisco Secure ACS is installed:
- From the Cisco Secure ACS command-line interface (CLI), issue the show version command, as shown in the following example:
acs51a/admin# show version
Cisco Application Deployment Engine OS Release: 1.2
ADE-OS Build Version: 126.96.36.199
ADE-OS System Architecture: i386
Copyright (c) 2005-2009 by Cisco Systems, Inc.
All rights reserved.
Version information of installed applications
Cisco ACS VERSION INFORMATION
Version : 188.8.131.52.6
Internal Build ID : B.2347
- On the main login page of the Cisco Secure ACS web-based interface, the version information is displayed on the left side of the screen.
- From the Cisco Secure ACS web-based interface, log in and click the About link at the top right corner of the screen.
Cisco Secure ACS version 5.1 will identify itself as version 184.108.40.206, whereas Cisco Secure ACS version 5.2 will identify itself as version 220.127.116.11. The presence of an additional digit after the version number indicates the highest patch level installed. For example, a version number of 18.104.22.168.3 indicates Cisco Secure ACS version 5.1 with up to patch 3 installed. The absence of any additional digit after the version string indicates a Cisco Secure ACS version with no patches installed.
The following Cisco Secure ACS versions are not affected by this vulnerability:
- Any Cisco Secure ACS version prior to version 5.1
- Cisco Secure ACS version 5.1 without any patches installed, or with patch 6 or later installed
- Cisco Secure ACS version 5.1 with patch 1 or 2 (or both of these patches) installed
- Cisco Secure ACS version 5.1 with patch 3, 4, or 5 (or any combination of these patches) installed, as long as patch 6 or later is also installed
- Cisco Secure ACS version 5.2 with patch 1 or 2 (or both of these patches) installed, as long as patch 3 or later is also installed
- Cisco Secure ACS version 5.2 with patch 3 or later installed
The previous list applies to both the hardware appliance and the software-only versions of the product.
No other Cisco products are currently known to be affected by this vulnerability.
Cisco Secure ACS operates as a centralized RADIUS and TACACS+ server, combining user authentication, user and administrator device access control, and policy control into a centralized identity networking solution.
A vulnerability exists in some Cisco Secure ACS versions that could allow a remote, unauthenticated attacker to change the password of any user account to any value without providing the account's previous password. Successful exploitation requires the user account to be defined on the internal identity store.
This vulnerability cannot be used to change the password for the following types of users accounts:
- User accounts that are defined on external identity stores such as a Lightweight Directory Access Protocol (LDAP) server, a Microsoft Active Directory server, an RSA SecurID server, or an external RADIUS server
- System administrator accounts for the Cisco Secure ACS server itself that have been configured through the web-based interface
- Users accounts for the Cisco Secure ACS server itself that have been configured through the username username password password CLI command
This vulnerability does not allow an attacker to perform any other changes to the ACS database. That is, an attacker cannot change access policies, device properties, or any user attributes except the user password.
This vulnerability is documented in Cisco bug ID CSCtl77440 ( registered customers only) and has been assigned the CVE identifier CVE-2011-0951.
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
Cisco has also provided a CVSS calculator to help compute the environmental impact for individual networks at
CSCtl77440 - Able to arbitrarily change user account passwords
Calculate the environmental score of CSCtl77440
CVSS Base Score - 5.0
CVSS Temporal Score - 4.4
Successful exploitation of this vulnerability could allow an attacker to change the password of any user account that is defined on the internal identity store. After the password has been changed, an attacker could use those credentials to impersonate the user. Because the user would not know the new password, the attacker could also prevent a user from authenticating.
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.
This vulnerability is first fixed in the following Cisco Secure ACS software patches:
- Cisco Secure ACS version 5.1
File 5-1-0-44-6.tar.gpg - ACS 22.214.171.124 cumulative patch 6
- Cisco Secure ACS version 5.2
File 5-2-0-26-3.tar.gpg - ACS 126.96.36.199 cumulative patch 3
These Cisco Secure ACS patches can be downloaded from the Software Center on Cisco.com by visiting http://www.cisco.com/cisco/software/navigator.html (registered customers only). The patches are accessible using the following paths:
- "Security > Identity Management > Cisco Secure Access Control System > Cisco Secure Access Control System 5.1"
- "Security > Identity Management > Cisco Secure Access Control System > Cisco Secure Access Control System 5.2"
There is no workaround for this vulnerability.
The attack surface can be limited by allowing only a known, limited set of management stations to access the Cisco Secure ACS web-based management interface. Those access control rules can be configured on the device itself by following the instructions in the "Configuring Administrator Access Settings" section of the "Managing System Administrators" chapter of the Cisco Secure ACS User Guide, which is available at http://www.cisco.com/en/US/docs/net_mgmt/cisco_secure_access_control_system/5.1/user/guide/admin_admin.html#wp1069174 .
Cisco Secure ACS provides an optional User Change Password (UCP) web service. Customers can implement the UCP functionality through either a web-based front-end application or a scripting interface. In either case, the computer that offers the UCP services to clients needs access to TCP port 443 on the ACS server in order to perform such password changes. Because this access would allow exploitation of the vulnerability described in this advisory, both of the following recommendations apply:
- Stop providing UCP services
- Do not include any computer that offers UCP services (either web-based or scripted) in the set of management stations that are allowed to access the ACS server
Additional mitigations that can be deployed on Cisco devices within the network are available in the companion document "Cisco Applied Mitigation Bulletin: Identifying and Mitigating Exploitation of the Cisco Secure Access Control System Unauthorized Password Change Vulnerability", which is available at the following location: http://tools.cisco.com/security/center/content/CiscoAppliedMitigationBulletin/cisco-amb-20110330-acs.
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
, or as otherwise set forth at Cisco.com Downloads at
Do not contact firstname.lastname@example.org or email@example.com for software upgrades
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
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 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: firstname.lastname@example.org
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.
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.
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This advisory is posted on Cisco's worldwide website at:
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.
Initial public release.