Products & Services

Multiple Vulnerabilities in Cisco Secure Access Control Server

Advisory ID: cisco-sa-20040825-acs

Revision 1.3

For Public Release 2004 August 25 16:00  UTC (GMT)


Cisco Secure Access Control Server for Windows (ACS Windows) and Cisco Secure Access Control Server Solution Engine (ACS Solution Engine) provide authentication, authorization, and accounting (AAA) services to network devices such as a network access server, Cisco PIX and a router. This advisory documents multiple Denial of Service (DoS) and authentication related vulnerabilities for the ACS Windows and the ACS Solution Engine servers.

The vulnerabilities are documented as these Cisco bug IDs:

This advisory will be posted at

Affected Products

This section provides details on affected products.

Vulnerable Products

These products are vulnerable:

CSCed81716 is only applicable to the ACS Solution Engine.

Successfully authenticate to your ACS box to determine your software revision. After you perform the authentication, the first screen displays the current ACS version in this format—CiscoSecure ACS Release 3.2(3) Build 11.

ACS versions may also be displayed as 003.002(003.011), where "011" is the build number referenced on the ACS graphical user interface (GUI).

Products Confirmed Not Vulnerable

Cisco Secure ACS for UNIX is not affected by these vulnerabilities. No other Cisco products are currently known to be affected by these vulnerabilities.


The Cisco Secure ACS products provide a centralized identity networking solution and simplified user management experience across all Cisco devices and security management applications. The products help to ensure enforcement of assigned policies—they allow network administrators to control who can log into the network, per user privileges in the network, security auditing and billing information, and command level access controls.

  • CSCeb60017 ( registered customers only) and CSCec66913 ( registered customers only) -- Cisco Secure ACS provides a Web-based management interface, termed CSAdmin, which listens on TCP port 2002. When flooded with TCP connections the ACS Windows and ACS Solution Engine stops responding to any new TCP connections destined for port 2002. Additionally, services on the ACS that process authentication related requests may become unstable and stop responding, which hampers the ability for ACS to process any authentication related requests. A reboot of the device is required to restore these services.
  • CSCec90317 ( registered customers only) -- Cisco Secure ACS, when configured for Light Extensible Authentication Protocol (LEAP) RADIUS Proxy, forwards LEAP authentication requests to a secondary RADIUS server. The ACS device with LEAP RADIUS proxy configured may crash when LEAP authentication requests are being processed. A reboot is required to bring the device back to an operational state.
  • CSCed81716 ( registered customers only) -- Cisco Secure ACS can communicate with external databases and authenticate users against those databases. One of the external databases that ACS supports is Novell Directory Services (NDS). If an anonymous bind in NDS is allowed, and if the ACS Solution Engine is authenticating NDS users with NDS as the external database and not Generic LDAP, then users are able to authenticate with blank passwords against that NDS database. However, wrong passwords and incorrect usernames are properly rejected.
  • CSCef05950 ( registered customers only) -- Once a user successfully authenticates to the ACS GUI on TCP port 2002, a separate TCP connection is created between the browser and ACS administration Web service, with a random destination port. If an attacker spoofs the IP address of the user computer, and accesses the ACS GUI on this random port, then the attacker may be able to connect to the ACS GUI, bypassing authentication. Authentication to the ACS server may also be bypassed if the attacker is behind the same PAT device as that of the ACS user and accesses the ACS GUI on this random port.

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 .

Cisco has also provided a CVSS calculator to help compute the environmental impact for individual networks at .


This section describes the impact of these vulnerabilities.

  • CSCeb60017 ( registered customers only) , CSCec66913 ( registered customers only) , and CSCec90317 ( registered customers only) -- Exploitation of these vulnerabilities may cause a shutdown of core services, impacting the availability of services on the ACS devices, which will persist until the device is rebooted. This results in a Denial of Service for the ACS device, which can potentially cause authentication to be bypassed, depending on the configuration of AAA clients within the network.
  • CSCed81716 ( registered customers only) -- This vulnerability may allow unauthorized users to access AAA clients without an effective password (using blank passwords) if the bind to the NDS database is anonymous.
  • CSCef05950 ( registered customers only) -- This vulnerability may allow unauthenticated users to gain access to the ACS Administration GUI.

Software Versions and Fixes

When considering software upgrades, also consult 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.


Impacted Versions

Fixed Versions


CSCeb60017 ( registered customers only)

3.2(1), 3.2(2)

003.002(002.020) or later, 3.2(3) in Product Upgrade Tool

ACS Windows and ACS Solution Engine

CSCec66913 ( registered customers only)

3.2(1), 3.2(2)

003.002(002.020) or later, 3.2(3) in Product Upgrade Tool

ACS Windows and ACS Solution Engine

CSCec90317 ( registered customers only)


003.002(002.005) or later, 3.2(2) in Product Upgrade Tool

ACS Windows and ACS Solution Engine

CSCed81716 ( registered customers only)

3.2(1), 3.2(2)

003.002(003.011) or later, 3.2(3) in Product Upgrade Tool

ACS Solution Engine only

CSCef05950 ( registered customers only)

3.0(x), 3.1(x), 3.2(x), 3.3(1)

There are patches available to address this vulnerability for versions 3.1(2), 3.2(3) and 3.3(1). See the Customers with Service Contracts section below for details on the location of these patches.

Although version 3.0 is affected, the fix is only available with a feature set included in versions 3.1 and higher. Customers without Service Contracts will need to contact Cisco Technical Assistance Center at the numbers listed below for assistance.

ACS Windows and ACS Solution Engine

Upgrade procedures can be found as indicated:


This section describes workarounds for these vulnerabilities.

  • Configure an IP address filter on ACS Windows and ACS Solution Engine to limit the exposure of these vulnerabilities. From within the ACS GUI, browse to Administration Control > Access Policy to limit access to only the machines that need to administer the ACS remotely.
  • Apply access control lists (ACLs) on routers, switches and firewalls that filter traffic to the ACS so that traffic is only allowed from stations that need to remotely administer the box. Refer to for examples on how to apply ACLs on Cisco routers.
  • As a best practice, use HTTPS to limit access to the Cisco ACS GUI. Issues detailed in CSCef05950 ( registered customers only) still exist when you use HTTP instead of HTTPS to access the Cisco ACS GUI.

Refer to /en/US/products/sw/secursw/ps2086/products_user_guide_chapter09186a0080205a43.html#wp89030 for information on how to set up an access policy on the Cisco ACS.

Obtaining Fixed Software

Cisco has made free software available to address this vulnerability for affected customers. 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 Downloads at

Do not contact either "" or "" 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

Customers using Third Party Support Organizations

Customers whose Cisco products are provided or maintained through prior or existing agreement 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 who 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 obtain software patches and bug fixes 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:

Have your product serial number available and provide the URL of this notice as evidence of entitlement to a software patch or bug fix. Customers without service contracts should request a software patch or bug fix through the TAC.

Refer to for additional TAC contact information, including special 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.

Status of this Notice: Final


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.


This advisory will be 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.

  • (includes CERT/CC)

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 1.3


Fixed link.

Revision 1.2


Clarified impact of Denial of Service vulnerabilities in the Impact section. Added the Impacted Versions column and added content to the Fixed Versions column in the Software Versions and Fixes section table. Clarified version 3.0(x) status in the Software Versions and Fixes section.

Revision 1.1


Changed URLs in the Obtaining Fixed Software section.

Revision 1.0


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 This includes instructions for press inquiries regarding Cisco security notices. All Cisco security advisories are available at