A vulnerability in the forwarding information base (FIB) code of Cisco IOS XR Software could allow an unauthenticated, remote attacker to cause inconsistency between the routing information base (RIB) and the FIB, resulting in a denial of service (DoS) condition. The vulnerability is due to incorrect processing of extremely long routing updates. An attacker could exploit this vulnerability by sending a large routing update. A successful exploit could allow the attacker to trigger inconsistency between the FIB and the RIB, resulting in a DoS condition. Cisco Bug IDs: CSCus84718.