full-disclosure - [FD] Trojan-Downloader.Win32.Delf.ur / Insecure Permissions

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Message-ID: <CAAHK0WTtngiQy7Jr8XmGuT0uKcxm__2UoXJ7g9ESmWU6SAUvSQ@mail.gmail.com>
Date: Thu, 1 Apr 2021 14:19:35 -0400
From: malvuln <malvuln13@...il.com>
To: fulldisclosure@...lists.org
Subject: [FD] Trojan-Downloader.Win32.Delf.ur / Insecure Permissions

Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source:
https://malvuln.com/advisory/5b63a6e730f094d182c9030e3a57bcb8.txt
Contact: malvuln13@...il.com
Media: twitter.com/malvuln

Threat: Trojan-Downloader.Win32.Delf.ur
Vulnerability: Insecure Permissions
Description: Win32.Delf.ur creates an insecure dir named "Messenger" under
c:\ drive and grants change (C) permissions to the authenticated user
group. Standard users can rename the executables 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: 5b63a6e730f094d182c9030e3a57bcb8
Vuln ID: MVID-2021-0155
Dropped files: msn.DLL, msn.exe
Disclosure: 04/01/2021

Exploit/PoC:
C:\>cacls Messenger
C:\Messenger BUILTIN\Administrators:(OI)(CI)(ID)F
             NT AUTHORITY\SYSTEM:(OI)(CI)(ID)F
             BUILTIN\Users:(OI)(CI)(ID)R
             NT AUTHORITY\Authenticated Users:(ID)C
             NT AUTHORITY\Authenticated Users:(OI)(CI)(IO)(ID)C

C:\>dir Messenger
 Volume in drive C has no label.

 Directory of C:\Messenger

03/30/2021  08:07 PM            25,600 msn.DLL
06/16/2012  03:54 AM            62,464 msn.exe
               2 File(s)         88,064 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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