Discovery / credits: Malvuln (John Page aka hyp3rlinx) (c) 2022
Original source: https://malvuln.com/advisory/5ac0f050f93f86e69026faea1fbb4450.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln

Threat: Trojan.Ransom.Ryuk.A
Vulnerability: Arbitrary Code Execution
Description: The ransomware 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. Once loaded the exploit dll will check if the current directory is "C:\Windows\System32", if not we grab our process ID and terminate. All basic tests were conducted successfully in a virtual machine environment.
Family: Ryuk
Type: PE32
MD5: 5ac0f050f93f86e69026faea1fbb4450
Vuln ID: MVID-2022-0640
Disclosure: 09/19/2022

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

#include "windows.h"

//By malvuln
//Purpose: Exploit Ryuk
/** 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 urlmon.c -m32
//gcc -shared -o urlmon.dll urlmon.o -m32

BOOL APIENTRY DllMain(HINSTANCE hInst, DWORD reason, LPVOID reserved){
  switch (reason) {
  case DLL_PROCESS_ATTACH:
   MessageBox(NULL, "Ryuk\nPWNED By MALVULN", "Code Exec PoC", 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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