Date: Sat, 7 May 2022 21:41:27 -0400
From: malvuln <malvuln13@...il.com>
To: fulldisclosure@...lists.org
Subject: [FD] Ransom.Conti / Code Execution

Discovery / credits: Malvuln (John Page aka hyp3rlinx) (c) 2022
Original source:
https://malvuln.com/advisory/20f0c736a966142de88dee06a2e4a5b1.txt
Contact: malvuln13@...il.com
Media: twitter.com/malvuln

Threat: Ransom.Conti
Vulnerability: Code Execution
Description: Conti 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 flaw 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: 20f0c736a966142de88dee06a2e4a5b1
Vuln ID: MVID-2022-0592
Disclosure: 05/07/2022
Video Poc URL: https://www.youtube.com/watch?v=hA6YGi8iobk

Exploit/PoC:
1) Compile the following C code as "netapi32.dll"
2) Place the DLL in same directory as the ransomware
3) Optional - Hide it: attrib +s +h "netapi32.dll"
4) Run the malware

#include "windows.h"

//By malvuln
//Purpose: Exploit Conti
//MD5: 20f0c736a966142de88dee06a2e4a5b1
/** 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 netapi32.c -m32
//gcc -shared -o netapi32.dll netapi32.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;
}


Disclaimer: The information contained within this advisory is supplied
"as-is" with no warranties or guarantees of fitness of use or otherwise.
Permission is hereby granted for the redistribution of this 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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