full-disclosure - [FD] Backdoor.Win32.VB.afu / Insecure Permissions

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Message-ID: <CAAHK0WRb7v-siOV0mKrdTTzZkg7indLkXet+48rjRPuoFGVoxw@mail.gmail.com>
Date: Fri, 5 Nov 2021 23:32:26 -0400
From: malvuln <malvuln13@...il.com>
To: fulldisclosure@...lists.org
Subject: [FD] Backdoor.Win32.VB.afu / Insecure Permissions

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

Disclaimer: The information contained within this advisory is supplied
"as-is" with no warranties or guarantees of fitness of use or otherwise.
Permission is hereby granted for the redistribution of this advisory,
provided that it is not altered except by reformatting it, and that due
credit is given. Permission is explicitly given for insertion in
vulnerability databases and similar, provided that due credit is given to
the author. The author is not responsible for any misuse of the information
contained herein and accepts no responsibility for any damage caused by the
use or misuse of this information. The author prohibits any malicious use
of security related information or exploits by the author or elsewhere. Do
not attempt to download Malware samples. The author of this website takes
no responsibility for any kind of damages occurring from improper Malware
handling or the downloading of ANY Malware mentioned on this website or
elsewhere. All content Copyright (c) Malvuln.com (TM).

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