Cisco NX-OS on the Nexus 1000V does not properly handle authentication for Virtual Ethernet Module (VEM) to Virtual Supervisor Module (VSM) communication, which allows remote attackers to obtain VEM access via (1) spoofed STUN packets or (2) a crafted VMware ESXi instance, aka Bug ID CSCud14832.
http://tools.cisco.com/security/center/content/CiscoSecurityNotice/CVE-2013-1211