Discovery / credits: Malvuln - malvuln.com (c) 2022
Original source: https://malvuln.com/advisory/96de05212b30ec85d4cf03386c1b84af.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln

Threat: Ransom.LockBit
Vulnerability: DLL Hijacking
Description: LockBit ransomware looks for and executes DLLs in its current directory. This can potentially allow us to 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. 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. All basic tests were conducted successfully in a virtual machine environment.
Family: LockBit
Type: PE32
MD5: 96de05212b30ec85d4cf03386c1b84af
Vuln ID: MVID-2022-0572
Disclosure: 05/02/2022
Video PoC URL: https://www.youtube.com/watch?v=3i6tv4cpfSc

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

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

//By malvuln - 5/1/2022
//Vuln: DLL Hijacking
//Target: Lockbit Ransomware
//MD5: 96de05212b30ec85d4cf03386c1b84af
/** 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));
   //printf("Current directory: %s\n", buf);
   //check the path, netapi32.dll is sideloaded by lockbit
   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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