full-disclosure - [FD] Backdoor.Win32.Bifrose.ahyg / Insecure Permissions

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Message-ID: <CAAHK0WTp9xF-Sr3T2AU-V+9=yvG7jVxtweXJZfu+CuBUqJWB4Q@mail.gmail.com>
Date: Tue, 5 Oct 2021 19:58:14 -0400
From: malvuln <malvuln13@...il.com>
To: fulldisclosure@...lists.org
Subject: [FD] Backdoor.Win32.Bifrose.ahyg / Insecure Permissions

Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source:
https://malvuln.com/advisory/d6aff119c03ff378d386b30b36b07a69.txt
Contact: malvuln13@...il.com
Media: twitter.com/malvuln

Threat: Backdoor.Win32.Bifrose.ahyg
Vulnerability: Insecure Permissions
Description: The malware creates an dir 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: d6aff119c03ff378d386b30b36b07a69
Vuln ID: MVID-2021-0356
Dropped files: vfenr522008a.exe
Disclosure: 10/04/2021

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

 Directory of C:\Temp

10/03/2021  01:40 AM           689,664 vfenr522008a.exe
               1 File(s)        689,664 bytes

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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
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