Cisco Network Admission Control (NAC) Appliance 3.5.x, 3.6.x before 3.6.4.4, 4.0.x before 4.0.6, and 4.1.x before 4.1.2 allows remote attackers to obtain the shared secret for the Clean Access Server (CAS) and Clean Access Manager (CAM) by sniffing error logs.

The Cisco Network Admission Control (NAC) 3.6.4.1 and earlier allows remote attackers to prevent installation of the Cisco Clean Access (CCA) Agent and bypass local and remote protection mechanisms by modifying (1) the HTTP User-Agent header or (2) the behavior of the TCP/IP stack. NOTE: the vendor has disputed the severity of this issue, stating that users cannot bypass authentication mechanisms.