Date: Tue, 3 May 2022 09:01:22 -0400
From: malvuln <malvuln13@...il.com>
To: fulldisclosure@...lists.org
Subject: [FD] REvil Ransom / Code Execution

Discovery / credits: Malvuln - malvuln.com (c) 2022
Original source:
https://malvuln.com/advisory/7d7ee58c2696794b3be958b165eb61a9.txt
Contact: malvuln13@...il.com
Media: twitter.com/malvuln

Threat: REvil Ransom
Vulnerability: Code Execution
Description: REvil looks for and executes DLLs in its current
directory. Therefore, we can potentially hijack a vuln DLL execute our
own code, control and terminate the malware pre-encryption. The
exploit dll will check if the current directory is
"C:\Windows\System32", if not we grab our process ID and terminate. We
do not need to rely on hash signature or third-party product, the
malwares own vulnerability 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: REvil
Type: PE32
MD5: 7d7ee58c2696794b3be958b165eb61a9
Vuln ID: MVID-2022-0577
Disclosure: 05/03/2022
Video PoC URL: https://www.youtube.com/watch?v=WnDxcYzfbUQ

Exploit/PoC:
1) Compile the following C code as "CLDAPI.dll"
2) Place the DLL in same directory as the ransomware
3) Optional - Hide it: attrib +s +h "CLDAPI.dll"
4) Run Conti

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

//By malvuln
//Purpose: Code Execution
//Target: REvi Ransomware
//MD5: 7d7ee58c2696794b3be958b165eb61a9
/** 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 CLDAPI.c -m32
//gcc -shared -o CLDAPI.dll CLDAPI.o -m32

BOOL APIENTRY DllMain(HINSTANCE hInst, DWORD reason, LPVOID reserved){
  switch (reason) {
  case DLL_PROCESS_ATTACH:
   MessageBox(NULL, "Code Exec", "by malvuln", MB_OK);
   TCHAR buf[MAX_PATH];
   GetCurrentDirectory(MAX_PATH, TEXT(buf));
   int rc = strcmp("C:\\Windows\\System32", TEXT(buf));
   	if(rc != 0){
   	HANDLE handle = OpenProcess(PROCESS_TERMINATE, FALSE, getpid());
     if (NULL != handle) {
        TerminateProcess(handle, 0);
       CloseHandle(handle);
     }
   }
    break;
  }
  return TRUE;
}


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advisory, provided that it is not altered except by reformatting it,
and that due credit is given. Permission is explicitly given for
insertion in vulnerability databases and similar, provided that due
credit is given to the author. The author is not responsible for any
misuse of the information contained herein and accepts no
responsibility for any damage caused by the use or misuse of this
information. The author prohibits any malicious use of security
related information or exploits by the author or elsewhere. Do not
attempt to download Malware samples. The author of this website takes
no responsibility for any kind of damages occurring from improper
Malware handling or the downloading of ANY Malware mentioned on this
website or elsewhere. All content Copyright (c) Malvuln.com (TM).
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