VMware ESXi 3.5 through 5.0 and ESX 3.5 through 4.1 allow remote attackers to execute arbitrary code or cause a denial of service (memory overwrite) via NFS traffic.
http://www.securityfocus.com/bid/53371
http://www.securitytracker.com/id?1027018
http://www.vmware.com/security/advisories/VMSA-2012-0009.html