Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/c6ba7fcb9eb9bdd7e081e2e84e784dcb.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln

Threat: Backdoor.Win32.VB.afu
Vulnerability: Insecure Permissions
Description:  The malware writes an .EXE with insecure permissions under c:\ drive granting change (C) permissions to the authenticated user group. Standard users can rename the executable dropped by the malware to disable it or replace it with their own executable. Then wait for a privileged user to logon to the infected machine to potentially escalate privileges.
Type: PE32
MD5: c6ba7fcb9eb9bdd7e081e2e84e784dcb
Vuln ID: MVID-2021-0391
Dropped files: Explorer.exe 
Disclosure: 11/05/2021


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


C:\>dir /a \Explorer.exe
 Volume in drive C has no label.

 Directory of C:\

06/16/2012  12:55 AM           222,195 Explorer.exe
               1 File(s)        222,195 bytes


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