Finally Terminate


void __cdecl FUN_00401d0a(_EXCEPTION_POINTERS *param_1)

{
  HANDLE hProcess;
  UINT uExitCode;
 
  SetUnhandledExceptionFilter((LPTOP_LEVEL_EXCEPTION_FILTER)0x0);
  UnhandledExceptionFilter(param_1);
  uExitCode = 0xc0000409;
  hProcess = GetCurrentProcess();
  TerminateProcess(hProcess,uExitCode);
  return;
}



💥 Yep — hard stop confirmed.

This final function, FUN_00401d0a(), is the termination endpoint for the entire stack-protection failure pathway. Let's walk it out real clean:

🔥 What Does FUN_00401d0a() Do?

void __cdecl FUN_00401d0a(_EXCEPTION_POINTERS *param_1)

This function:

  1. Removes any installed exception filters:

    SetUnhandledExceptionFilter(NULL);

  2. Passes the fake exception to Windows' default handler:

    UnhandledExceptionFilter(param_1);

    • This is where you'd get a crash dialog.

    • Or, if WER (Windows Error Reporting) is enabled, the dump/report is generated here.

  3. Immediately terminates the process:

    TerminateProcess(GetCurrentProcess(), 0xC0000409);

    • 0xC0000409 = STATUS_STACK_BUFFER_OVERRUN

    • This is not recoverable — Windows considers it a security-critical exception.

💀 TL;DR — Full Flow

You're now seeing the full MSVC CRT buffer overrun protection sequence:

🔐 Stack Smashing Detected (Cookie mismatch):

➡️ FUN_00401ccb()
→ detects corruption →
➡️ calls FUN_00401d32()
→ builds fake _EXCEPTION_POINTERS, marks as 0xC0000409 →
➡️ calls FUN_00401d0a()
→ triggers WER/crash report, and immediately
➡️ calls TerminateProcess()

🤔 Why All the Ceremony?

Because this is security.

  • MSVC doesn't trust return or SEH at this point — the stack might be corrupted.

  • So it uses int 0x29 (fast-fail) or a controlled TerminateProcess() to halt.

This avoids letting malicious code run after a buffer overflow.

✅ TL;DR²

Function Purpose
FUN_00401ccb Validates stack guard cookie
FUN_00401d32 Assembles fake exception/context, mimics real crash
FUN_00401d0a Invokes default Windows handler, then kills the process cold

You're now looking at the final stage of the MSVC stack corruption response system.

Let me know if you want to map this to symbols (like __report_gsfailure()), or you're curious how you could bypass or hook this for reverse engineering/debugging. 😈


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