Windows Hyper-V Denial of Service Vulnerability. By sending a specially crafted message to the Hyper-V host virtualization stack, a guest VM could cause a reference count in the host virtualization stack to be leaked. In most circumstances, this would result in a memory leak on the Hyper-V host. If the leaked reference count value were to overflow, reference count hardening built-in to the Hyper-V virtualization stack would cause the host to bugcheck (crash) in a controlled manner, mitigating this issue against exploitation for code execution or privilege elevation.