Race condition in Cisco Adaptive Security Appliance (ASA) 7.0(0), 7.0(2), and 7.0(4), when running with an Active/Standby configuration and when the failover LAN interface fails, allows remote attackers to cause a denial of service (standby firewall failure) by sending spoofed ARP responses from an IP address of an active firewall, which prevents the standby firewall from becoming active, aka "failover denial of service."