Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/04a5a52f12d2a130bb88f98c3bc14aa8.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln

Threat: Trojan-Dropper.Win32.Dycler.yhb
Vulnerability: Insecure Permissions
Description: Dycler.yhb creates a dir named "RECYCLER" under c:\ drive and grants change (C) permissions to the authenticated user group. Standard users can rename the "cft_mon.exe" 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: 04a5a52f12d2a130bb88f98c3bc14aa8
Vuln ID: MVID-2021-0140
Dropped files: cft_mon.exe
Disclosure: 03/23/2021


Exploit/PoC:
C:\>cacls \RECYCLER
C:\RECYCLER 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 \RECYCLER

C:\RECYCLER>dir /a
 Volume in drive C has no label.

 Directory of C:\RECYCLER

06/17/2012  01:56 AM           463,591 cft_mon.exe
               1 File(s)        463,591 bytes



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