Hyper-V in Microsoft Windows Server 2008 Gold, SP2, R2, and R2 SP1 allows guest OS users to cause a denial of service (host OS infinite loop) via malformed machine instructions in a VMBus packet, aka "VMBus Persistent DoS Vulnerability."
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A12650
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2011/ms11-047