Windows Hyper-V in Windows 8.1, Windows Server 2012 Gold and R2, Windows RT 8.1, Windows 10 Gold, 1511, 1607, and 1703, and Windows Server 2016 allows a remote code execution vulnerability when it fails to properly validate input from a privileged user on a guest operating system, aka "Windows Hyper-V Remote Code Execution Vulnerability".
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2017-8664