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