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.