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; } 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).