VMware ESXi 4.0 through 5.1, and ESX 4.0 and 4.1, does not properly implement the Network File Copy (NFC) protocol, which allows man-in-the-middle attackers to cause a denial of service (unhandled exception and application crash) by modifying the client-server data stream.
Improper Input Validation The product receives input or data, but it does
not validate or incorrectly validates that the input has the
properties that are required to process the data safely and
correctly.