Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/3c5c6f0f6f78af12d6b76119696a4074.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln

Threat: Trojan-Downloader.Win32.Delf.nzg
Vulnerability: Insecure Permissions
Description: Win32.Delf.nzg creates an insecure dir named "Arquivos de Programas" 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: 3c5c6f0f6f78af12d6b76119696a4074
Vuln ID: MVID-2021-0157
Dropped files: npdsplay2.dll, Update.exe 
Disclosure: 04/01/2021

Exploit/PoC:
:\>cacls "Arquivos de Programas"
C:\Arquivos de Programas 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:\>cd "Arquivos de Programas"

C:\Arquivos de Programas>dir "Windows Media Player"
 Volume in drive C has no label.

 Directory of C:\Arquivos de Programas\Windows Media Player

03/31/2021  08:49 PM                 0 npdsplay2.dll
               1 File(s)              0 bytes

C:\Arquivos de Programas>dir WindowsUpdate
 Volume in drive C has no label.

 Directory of C:\Arquivos de Programas\WindowsUpdate

03/31/2021  08:49 PM           198,144 Update.exe
               1 File(s)        198,144 bytes


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