As posted by vmware-security-alert@vmware.com on Bugtraq:

A vulnerability has been discovered in vmnat.exe on Windows hosts and vmnet-natd on Linux systems.
The vulnerability makes it possible for a malicious guest using a NAT networking configuration to execute unwanted code on the host machine.

AFFECTED SYSTEMS:
VMware Workstation, VMware GSX Server, VMware ACE, and VMware Player.

RESOLUTION:
VMware believes that the vulnerability is very serious, and recommends that affected users update their products to the new releases or change the configuration of the virtual machine so it does not use NAT networking.

The new releases are now available for download at www.vmware.com/download

If you choose not to update your product but want to ensure that the NAT service is not available, you can disable it completely on VMware Workstation or VMware GSX Server by following the instructions in the Knowledge Base article (Answer ID 2002) at http://www.vmware.com/support/kb.

FYI to all the VMWare users out there.