Memory protection bypass via unintercepted HFI MSR writes

Hyper-V in affected Microsoft Windows builds allows local users to bypass protected physical-memory restrictions through HFI controls. Hyper-V does not intercept root-partition writes to the HFI pointer and configuration MSRs, so the processor writes HFI data to a chosen physical page without enforcing EPT permissions. Exploitation requires HFI-capable 12th-generation or newer Intel hardware, arbitrary kernel-memory and MSR writes, and a shutdown or hibernation transition; successful use corrupts protected memory and can crash the system.