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


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