Watchguard Firebox II contains a flaw that may allow a remote denial of service. The issue is due to the kernel of Firebox II not properly handling malformed TCP or ICMP packets. By sending a large stream (>10,000) of malformed ICMP or TCP packets, a remote attacker can crash or reboot the system, resulting in loss of availability.
Upgrade to version 4.6 or higher, as it has been reported to fix this vulnerability. An upgrade is required as there are no known workarounds.