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 as 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 the DLL that 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.
0cfd4ed7809eaa6bf784adff2f043dc32b8327dd12669f01b586f7bbc080223cDiscovery / credits: Malvuln (John Page aka hyp3rlinx) (c) 2022
Original source: https://malvuln.com/advisory/8ca35b7867e23a1bbb0fea6d51fc1b61.txt
Contact: [email protected]
Media: twitter.com/malvuln
Threat: Ransom.REvil
Vulnerability: Code Execution
Description: 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: REvil
Type: PE32
MD5: 8ca35b7867e23a1bbb0fea6d51fc1b61
Vuln ID: MVID-2022-0596
Disclosure: 05/12/2022
Exploit/PoC:
1) Compile the following C code as "winhttp.dll" 32-bit
2) Place the DLL in same directory as the ransomware
3) Optional - Hide it: attrib +s +h "winhttp.dll"
4) Run the malware
#include "windows.h"
//By malvuln
//gcc -c winhttp.c -m32
//gcc -shared -o winhttp.dll winhttp.o -m32
//Purpose: Exploit REvil
/** 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, "REvil\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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