A vulnerability in the password change feature of Cisco Firepower Management Center (FMC) software could allow an unauthenticated, remote attacker to determine valid user names on an affected device. This vulnerability is due to improper authentication of password update responses. An attacker could exploit this vulnerability by forcing a password reset on an affected device. A successful exploit could allow the attacker to determine valid user names in the unauthenticated response to a forced password reset.