full-disclosure - [FD] HEUR.Trojan.Win32.Bayrob.gen / Insecure Permissions

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Message-ID: <CAAHK0WTB=KvYbKXdMVfNbbnN6hsFKiYEH4cgLdWCQOFZokwBaw@mail.gmail.com>
Date: Thu, 29 Apr 2021 19:03:46 -0400
From: malvuln <malvuln13@...il.com>
To: fulldisclosure@...lists.org
Subject: [FD] HEUR.Trojan.Win32.Bayrob.gen / Insecure Permissions

Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source:
https://malvuln.com/advisory/765698ccfb033c86eea6d293235d7ed0.txt
Contact: malvuln13@...il.com
Media: twitter.com/malvuln

Threat: HEUR.Trojan.Win32.Bayrob.gen
Vulnerability: Insecure Permissions
Description:  The malware creates a insecure dir named "rlpzeasjvgnb" 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: 765698ccfb033c86eea6d293235d7ed0
Vuln ID: MVID-2021-0191
Dropped files: mv4aefb186aghbtwsvxglk3h.exe, btqq2r, gzjegrkpac, qaazfq
Disclosure: 04/29/2021

Exploit/PoC:
C:\>cacls rlpzeasjvgnb
C:\rlpzeasjvgnb 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 rlpzeasjvgnb
 Volume in drive C has no label.

 Directory of C:\rlpzeasjvgnb

04/25/2021  12:21 AM                 4 btqq2r
04/25/2021  12:20 AM                 0 gzjegrkpac
04/25/2021  12:20 AM           222,208 mv4aefb186aghbtwsvxglk3h.exe
04/25/2021  12:20 AM                 6 qaazfq
               4 File(s)        222,218 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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