Discovery / credits: Malvuln (John Page aka hyp3rlinx) (c) 2022
Original source: https://malvuln.com/advisory/2aea3b217e6a3d08ef684594192cafc8.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln

Threat: Ransom.Cryakl
Vulnerability: Code Execution
Description: Cryakl looks for and loads a DLL named "wow64log.dll" in Windows\System32. Therefore, we can drop our own DLL to intercept and terminate the malware pre-encryption. The exploit dll will simply display a Win32API message box and call exit(). The exploit DLL must export "InterlockedExchange" function or it fails with error. We do not need to rely on hash signature or third-party product, the malware will do the work for us. Endpoint protection systems and or antivirus can potentially be killed prior to executing malware, but this method cannot as theres nothing to kill the DLL just lives on disk waiting. From defensive perspective you can add the DLLs to a specific network share containing important data as a layered approach. All basic tests were conducted successfully in a virtual machine environment.
Family: Cryakl
Type: PE32
MD5: 2aea3b217e6a3d08ef684594192cafc8
Vuln ID: MVID-2022-0590
Disclosure: 05/06/2022
Video PoC URL: https://www.youtube.com/watch?v=uI7kr8gFTP4

Exploit/PoC:
1) Compile the following C code as "wow64log.dll" as x64
2) Place the DLL in Windows\System32
3) Run the malware

#include "windows.h"

//By malvuln 
//Purpose: Exploit Ransom.Cryakl
//MD5: 2aea3b217e6a3d08ef684594192cafc8
/** DISCLAIMER:
Author is NOT responsible for any damages whatsoever by using this software or improper malware
handling. By using this code you assume and accept all risk implied or otherwise.
**/

//compile as x64
//gcc -c wow64log.c 
//gcc -shared -o wow64log.dll wow64log.o 
//DLL must live under Windows\System32 dir

BOOL APIENTRY DllMain(HINSTANCE hInst, DWORD reason, LPVOID reserved){
  switch (reason) {
  case DLL_PROCESS_ATTACH:
   MessageBox(NULL, "Code Exec", "by malvuln", MB_OK);
   exit(0);
    break;
  }
  return TRUE;
}

extern __declspec(dllexport) WINBASEAPI LONG WINAPI InterlockedExchange (LONG volatile *Target, LONG Value){
    exit(1);
}


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