VMware vCenter Server Appliance (vCSA) 5.5 before Update 2, 5.1 before Update 3, and 5.0 before Update 3c does not properly validate certificates when connecting to a CIM Server on an ESXi host, which allows man-in-the-middle attackers to spoof CIM servers via a crafted certificate.
http://www.vmware.com/security/advisories/VMSA-2014-0012.html
http://www.securityfocus.com/archive/1/534161/100/0/threaded