VMSA-2012-0012 is an advisory specific to a VMware ESXi update that addresses several security issues.

This includes an ESXi update to third party component libxml2. The libxml2 third party library has been updated which addresses multiple security issues.

All the details are available here: http://www.vmware.com/security/advisories/VMSA-2012-0012.html

Russ McRee | @holisticinfosec