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.

A stack-based buffer overflow exists in the way the CSRadius service handles certain RADIUS Accounting-Request packets. This vulnerability may allow a remote attacker with the ability to craft RADIUS packets to execute arbitrary code or 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 this issue. 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 required to exploit this vulnerability.

A remote attacker with prior access to the shared RADIUS secret key material may be able to execute arbitrary code on an affected system or cause the CSRadius service on that system to crash. The attacker-supplied code would be executed with the privileges of the CSRadius service, typically Local System.

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 the software, are encouraged to review the workarounds described in Cisco Security Advisory cisco-sa-20070105-csacs.