full-disclosure - [FD] Win32.Ransom.BlueSky / Arbitrary Code Execution

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Date: Sat, 13 Aug 2022 02:00:19 -0400
From: malvuln <malvuln13@...il.com>
To: fulldisclosure@...lists.org
Subject: [FD] Win32.Ransom.BlueSky / Arbitrary Code Execution

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

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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