telnetd in Cisco IOS XR 5.0.1 on Network Convergence System 6000 devices allows remote attackers to cause a denial of service (device reload) via a malformed TELNET packet, aka Bug ID CSCuq31566.
Cisco IOS XR 5.1 and earlier on Network Convergence System 6000 devices allows remote attackers to cause a denial of service (NPU and card hang or reload) via a malformed MPLS packet, aka Bug ID CSCuq10466.