int main() HMODULE hNtdll = GetModuleHandleW(L"ntdll.dll"); pNtQueryWnfStateData NtQueryWnfStateData = (pNtQueryWnfStateData)GetProcAddress(hNtdll, "NtQueryWnfStateData");
if (!pNtQueryWnfStateData) std::cerr << "Failed to find NtQueryWnfStateData export." << std::endl; return 1;
When analyzing system activity, using NtQueryWnfStateData provides significant advantages over traditional approaches like reading registry keys, parsing process memory, or using older system APIs. 1. High Performance and Low Overhead
: By corrupting WNF structures, attackers can often turn a simple bug into a full kernel read/write primitive. For example, in CVE-2021-31956 , WNF was used alongside NTFS extended attributes to achieve high-reliability privilege escalation. ntquerywnfstatedata ntdlldll better
To understand NtQueryWnfStateData , one must appreciate the critical role of ntdll.dll . This library is the ultimate link between a user-mode application and the Windows executive. Every time an application in user mode needs to perform a privileged operation (e.g., creating a file, allocating memory, or querying a WNF state), the request doesn't go directly to the kernel. Instead, the application calls a stub function in ntdll.dll . This stub prepares the system call number and arguments, then executes a special syscall instruction (or int 2e on older systems) to transition into kernel mode.
Because this function is undocumented by Microsoft, its prototype must be defined manually using native types from the Windows Driver Kit (WDK) or internal structural definitions:
As the API is not documented in standard SDKs, you must reverse-engineer its prototype to use it. By examining public headers and security research, its signature has been clearly established. The most accurate definition, found in sources like the wininc/ntexapi.h header used by the DynamoRIO project, is as follows: int main() HMODULE hNtdll = GetModuleHandleW(L"ntdll
The Windows Notification Facility is an internal kernel component that acts as the system’s notification backbone. WNF allows kernel drivers, system services, and user‑mode applications to publish and subscribe to state changes across the entire operating system.
[ User-Mode Application ] │ ▼ [ Win32 API / kernel32.dll ] (Standard Overhead) │ ▼ [ Native API / ntdll.dll ] (Direct System Calls) │ ▼ [ Windows Kernel Mode ]
ULONG lastStamp = 0; while (monitoring) ULONG newStamp = 0; ULONG dataSize = 0; NTSTATUS status = NtQueryWnfStateData(stateHandle, &lastStamp, NULL, 0, &dataSize, &newStamp); if (status == 0 && newStamp != lastStamp) // State changed, now fetch actual data with large buffer BYTE buffer[1024]; NtQueryWnfStateData(stateHandle, NULL, buffer, sizeof(buffer), NULL, NULL); ProcessStateChange(buffer); lastStamp = newStamp; For example, in CVE-2021-31956 , WNF was used
From a development perspective, understanding this mechanism can help you detect which optional features are active on a given system, which can be useful for compatibility testing and debugging.
: It retrieves the current data associated with a specific WNF State Name (identified by a 64-bit ID). WNF is a kernel-mode messaging system used by Windows components for inter-process communication (IPC).
if (NT_SUCCESS(pNtQueryWnfStateData(&WNF_SHEL_QUIETHOURS_ACTIVE_PROFILE_CHANGED, nullptr, // No type ID nullptr, // Default scope &changeStamp, &stateBuffer, &bufferSize))) std::cout << "Focus Assist state: "; switch (stateBuffer) case 0: std::cout << "Off" << std::endl; break; case 1: std::cout << "On (Priority only)" << std::endl; break; case 2: std::cout << "On (Alarms only)" << std::endl; break; default: std::cout << "Unknown state: " << stateBuffer << std::endl; break;