VMware Workstation 9.x before 9.0.1, VMware Player 5.x before 5.0.1, VMware Fusion 5.x before 5.0.1, VMware ESXi 4.0 through 5.1, and VMware ESX 4.0 and 4.1 allow guest OS users to cause a denial of service (VMX process disruption) by using an invalid port.