A vulnerability in the Common Access Card (CAC) authentication feature of Cisco Firepower Management Center (FMC) Software could allow an unauthenticated, remote attacker to bypass authentication and access the FMC system. The attacker must have a valid CAC to initiate the access attempt. The vulnerability is due to incorrect session invalidation during CAC authentication. An attacker could exploit this vulnerability by performing a CAC-based authentication attempt to an affected system. A successful exploit could allow the attacker to access an affected system with the privileges of a CAC-authenticated user who is currently logged in.