The Neighbor Discovery (ND) protocol implementation in the IPv6 stack on Cisco Adaptive Security Appliances (ASA) 5500 series devices with software 8.2(3) and earlier, and Cisco PIX Security Appliances devices, allows remote attackers to cause a denial of service (CPU consumption and device hang) by sending many Router Advertisement (RA) messages with different source addresses, as demonstrated by the flood_router6 program in the thc-ipv6 package, aka Bug ID CSCti24526.