A Deep Dive into the GetProcessHandleFromHwnd API

A deep technical analysis of the GetProcessHandleFromHwnd Windows API, tracing its evolution from Vista through Windows 11 24H2. The API began as a user-mode hook-based implementation in oleacc.dll, moved to a Win32k kernel function (NtUserGetWindowProcessHandle) in Windows 10 1803, and has undergone several security fixes. The kernel version introduced a critical vulnerability (CVE-2023-41772) by opening process handles with KernelMode access, bypassing all access checks. Subsequent versions partially fixed this but still allowed opening protected processes. Windows 11 24H2 introduced UIPI enforcement improvements and a new ResponsiblePid feature flag path that requires UI Access for all callers. The post also demonstrates how to exploit pre-24H2 systems to hijack a TCB-level protected process (WerFaultSecure.exe) by finding its window handle and calling the API to gain VM read/write access.