Discovery / credits: Malvuln - (John Page aka hyp3rlinx) (c) 2022  
Original source:  
Threat: Trojan.CryptoLocker  
Vulnerability: Code Execution  
Description: Cryptolocker drops a PE file in AppData\Roaming directory which then tries to load a DLL named "netapi32.dll". Therefore, we can drop our own DLL to intercept 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: CryptoLocker  
Type: PE32  
MD5: 209a288c68207d57e0ce6e60ebf60729  
Vuln ID: MVID-2022-0588  
Disclosure: 05/06/2022   
Video PoC URL:  
1) Compile the following C code as "netapi32.dll" 32bit  
2) Place the DLL in same directory as the ransomware  
3) Optional - Hide it: attrib +s +h "netapi32.dll"  
4) Run the malware  
#include "windows.h"  
//By malvuln - 5/6/2022  
//Purpose: Exploit CryptoLocker  
//gcc -c netapi32.c -m32  
//gcc -shared -o netapi32.dll netapi32.o -m32  
BOOL APIENTRY DllMain(HINSTANCE hInst, DWORD reason, LPVOID reserved){  
switch (reason) {  
MessageBox(NULL, "Code Exec", "by malvuln", MB_OK);  
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);  
return TRUE;  
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