Discovery / credits: Malvuln - malvuln.com (c) 2022
Original source: https://malvuln.com/advisory/710a77804637f65e22a2e230ff6444f9.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln

Threat: Conti.Ransom
Vulnerability: Code Execution
Description: Conti 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(). Our Conti.Ransom 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: Conti
Type: PE32
MD5: 710a77804637f65e22a2e230ff6444f9
SHA256: 0aaacd11d8b956d317489d060e72946d28ab6aef9be1b541aff9904a750f4b51
Vuln ID: MVID-2022-0579
Disclosure: 05/03/2022
Video PoC URL: https://www.youtube.com/watch?v=owsev3YTkWA

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

#include "windows.h"
#include "stdio.h"

//By malvuln - 5/2022
//MD5: 710a77804637f65e22a2e230ff6444f
//TARGET: Conti.Ransom
/** 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.
**/

//gcc -c wow64log.c 
//gcc -shared -o wow64log.dll wow64log.o 
//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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