Cisco Secure Access Control Server for Windows (ACS Windows) and Cisco Secure Access Control Server Solution Engine (ACS Solution Engine) 3.3.1, when the EAP-TLS protocol is enabled, does not properly handle expired or untrusted certificates, which allows remote attackers to bypass authentication and gain unauthorized access via a "cryptographically correct" certificate with valid fields such as the username.
https://exchange.xforce.ibmcloud.com/vulnerabilities/17936
http://www.securityfocus.com/bid/11577
http://www.cisco.com/warp/public/707/cisco-sa-20041102-acs-eap-tls.shtml