Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/ed1e47f62fa93f2fd2f4fbcfdd0f1c10.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln

Threat: Worm.Win32.Ngrbot.abpr
Vulnerability: Insecure Permissions 
Description: Ngrbot.abpr creates a dir named "Win.Msi" under c:\ drive and grants change (C) permissions to the authenticated user group. Standard users can rename several of 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: ed1e47f62fa93f2fd2f4fbcfdd0f1c10
Vuln ID: MVID-2021-0142
Dropped files: alg.exe, cssrs.exe,  System.exe, 
Disclosure: 03/24/2021


Exploit/PoC:
C:\>cacls C:\Win.Msi
C:\Win.Msi 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 Win.Msi

C:\Win.Msi>dir
 Volume in drive C has no label.

 Directory of C:\Win.Msi

05/30/2008  12:25 PM               132 3proxy.cfg
12/06/2011  11:56 AM           184,832 alg.exe
12/06/2011  11:59 AM           315,392 cssrs.exe
10/17/2011  12:37 PM               494 DiskDoctor.lnk
04/17/2009  07:40 AM           330,752 System.exe
               5 File(s)        831,602 bytes
               0 Dir(s)  15,876,706,304 bytes free


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