The HSRP implementation in Cisco NX-OS 6.2(2a) and earlier allows remote attackers to bypass authentication and cause a denial of service (group-member state modification and traffic blackholing) via malformed HSRP packets, aka Bug ID CSCup11309.
http://www.securitytracker.com/id/1030409
http://www.securityfocus.com/bid/67983
http://tools.cisco.com/security/center/viewAlert.x?alertId=34585
http://tools.cisco.com/security/center/content/CiscoSecurityNotice/CVE-2014-3295