Cisco IOS XR 4.3.4 and earlier on ASR 9000 devices, when bridge-group virtual interface (BVI) routing is enabled, allows remote attackers to cause a denial of service (chip and card hangs) via a series of crafted MPLS packets, aka Bug ID CSCuo91149.
http://www.securitytracker.com/id/1030597
http://tools.cisco.com/security/center/viewAlert.x?alertId=34936
http://tools.cisco.com/security/center/content/CiscoSecurityNotice/CVE-2014-3321