Cisco IOS XR 5.0.1 and 5.2.1 on Network Convergence System (NCS) 6000 devices and 5.1.3 and 5.1.4 on Carrier Routing System X (CRS-X) devices allows remote attackers to cause a denial of service (line-card reload) via malformed IPv6 packets with extension headers, aka Bug ID CSCuq95241.