Headline
REvil.Ransom Code Execution
REvil ransomware looks for and executes DLLs in its current directory. Therefore, we can hijack a DLL, execute our own code, and control and terminate the malware pre-encryption. The exploit DLL checks if the current directory is “C:\Windows\System32” and if not we grab our process ID and terminate. We do not need to rely on hash signatures or third-party products, the malware’s 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 as 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.
Discovery / credits: Malvuln - (John Page - aka hyp3rlinx) (c) 2022Original source: https://malvuln.com/advisory/4c5c1731481ea8d67ef6076810c49e00.txtContact: [email protected]: twitter.com/malvulnThreat: REvil.RansomVulnerability: Code ExecutionDescription: REvil 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: REvilType: PE32MD5: 4c5c1731481ea8d67ef6076810c49e00Vuln ID: MVID-2022-0583Disclosure: 05/05/2022Video PoC URL: https://www.youtube.com/watch?v=6LYBPP4N5yAExploit/PoC:1) Compile the following C code as "urlmon.dll" 32bit2) Place the DLL in same directory as the ransomware3) Optional - Hide it: attrib +s +h "urlmon.dll"4) Run the malware#include "windows.h"//By malvuln - 5/5/2022//Purpose: //gcc -c urlmon.c -m32//gcc -shared -o urlmon.dll urlmon.o -m32BOOL 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;}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).