The encryption functionality in Cisco NX-OS on the Nexus 1000V does not properly handle Virtual Supervisor Module (VSM) to Virtual Ethernet Module (VEM) communication, which allows remote attackers to intercept or modify network traffic by leveraging certain Layer 2 or Layer 3 access, aka Bug ID CSCud14691.
http://tools.cisco.com/security/center/content/CiscoSecurityNotice/CVE-2013-1208