Software Engineering Institute

Cisco Secure ACS is a Remote Access Dial-In User Service (RADIUS) and Terminal Access Controller Access Control System Plus (TACACS+) security server. The RADIUS protocol is handled by the CSRadius component of the Cisco Secure ACS product which is run as a service in Windows under the Local System account.

Several vulnerabilities, including a heap overflow in handling of the "Tunnel-Password" attribute, exist in the way the CSRadius service handles certain RADIUS Access-Request packets. These vulnerabilities may allow a remote attacker with the ability to craft RADIUS packets to cause the CSRadius service to crash.

Cisco states that versions of the Cisco Secure Access Control Server for Windows and Cisco Secure Access Control Server Solution Engine prior to 4.1 are affected by these issues. Cisco also states that the RADIUS secret key that is shared between the Network Access Server (NAS) and the Cisco Secure ACS server and/or appliance is not required to exploit these vulnerabilities.

A remote unauthenticated attacker may be able to cause the CSRadius service to crash, thereby causing a denial of service. Cisco states that these vulnerabilities will not allow an attacker to execute arbitrary code after successful exploitation.

Upgrade

Cisco has published Cisco Security Advisory cisco-sa-20070105-csacs in response to this issue. Users of affected software are encouraged to review this advisory and upgrade their software accordingly.

Workarounds

In addition to updated versions of the software, Cisco has published several workarounds for this issue. Users, particularly those who are unable to upgrade their software, are encouraged to review the workarounds described in Cisco Security Advisory cisco-sa-20070105-csacs.