Unspecified vulnerability in Cisco IOS 12.2SRE before 12.2(33)SRE4 15.0 and 15.1 and IOS XE 2.1.x through 3.3.x when an MPLS domain is configured allows remote attackers to cause a denial of service (device crash) via a crafted IPv6 packet related to an expired MPLS TTL aka Bug ID CSCto07919.