Cisco IOS XE 3.7S(.1) and earlier allows remote attackers to cause a denial of service (Packet Processor crash) via fragmented MPLS IP packets, aka Bug ID CSCul00709.
http://www.securitytracker.com/id/1029538
http://www.securityfocus.com/bid/64514
http://tools.cisco.com/security/center/viewAlert.x?alertId=32281
http://tools.cisco.com/security/center/content/CiscoSecurityNotice/CVE-2013-6981