A vulnerability in the RADIUS subsystem implementation of Cisco Secure Firewall Management Center (FMC) Software could allow an unauthenticated, remote attacker to inject arbitrary shell commands that are executed by the device.  This vulnerability is due to a lack of proper handling of user input during the authentication phase. An attacker could exploit this vulnerability by sending crafted input when entering credentials that will be authenticated at the configured RADIUS server. A successful exploit could allow the attacker to execute commands at a high privilege level. Note: For this vulnerability to be exploited, Cisco Secure FMC Software must be configured for RADIUS authentication for the web-based management interface, SSH management, or both.