Cisco NX-OS 5.0 and earlier on MDS 9000 devices allows remote attackers to cause a denial of service (supervisor CPU consumption) via Authentication Header (AH) authentication in a Virtual Router Redundancy Protocol (VRRP) frame, aka Bug ID CSCte27874.
http://tools.cisco.com/security/center/viewAlert.x?alertId=31663
http://tools.cisco.com/security/center/content/CiscoSecurityNotice/CVE-2013-5566