Ransom.CTBLocker / Code Execution

[malvuln <malvuln13 () gmail com>]

Discovery / credits: Malvuln - (John Page - aka hyp3rlinx) (c) 2022
Original source:
https://malvuln.com/advisory/de25f04dedaffde1be47ef26dc9a8176.txt
Contact: malvuln13 () gmail com
Media: twitter.com/malvuln

Threat: Ransom.CTBLocker
Vulnerability: Code Execution
Description: CTBLocker looks for and executes DLLs in its current
directory. Therefore, we can hijack a vuln DLL, execute our own code,
control and terminate the malware pre-encryption. The exploit dll checks 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 signatures or third-party
products, the malwares flaw does the work for us. Endpoint protection
systems and or antivirus can potentially be killed prior to executing
malware, but this method cannot as there's nothing to kill the DLL just
lives on disk waiting. From a 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: CTBLocker
Type: PE32
MD5: de25f04dedaffde1be47ef26dc9a8176
Vuln ID: MVID-2022-0586
Disclosure: 05/05/2022
Video PoC URL: https://www.youtube.com/watch?v=koXDYNI5ngQ


Exploit/PoC:
1) Compile the following C code as "SHFOLDER.DLL" 32bit
2) Place the DLL in same directory as the ransomware
3) Optional - Hide it: attrib +s +h "SHFOLDER.DLL"
4) Run the malware

#include "windows.h"

//By malvuln - 5/5/2022
//Purpose:
//gcc -c SHFOLDER.c -m32
//gcc -shared -o SHFOLDER.DLL SHFOLDER.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];
   if(GetCurrentDirectory(MAX_PATH, buf))
   if(strcmp("c:\\Windows\\system32", buf) != 0){
    HANDLE handle = OpenProcess(PROCESS_TERMINATE, FALSE, getpid());
     if (NULL != handle) {
        TerminateProcess(handle, 0);
       CloseHandle(handle);
     }
   }
    break;
  }
  return TRUE;
}



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