Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/06cbbff745c60c46e0996928c00ef28f.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln

Threat: Trojan-Dropper.Win32.Dycler.vrp
Vulnerability: Insecure Permissions
Description: Dycler.vrp creates an insecure dir named "Drivers" under c:\ drive and grants change (C) permissions to the authenticated user group. Standard users can rename the "pir.exe" file 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: 06cbbff745c60c46e0996928c00ef28f
Vuln ID: MVID-2021-0135
Dropped files: 72 id.bat, pir.exe
Disclosure: 03/19/2021


Exploit/PoC:
C:\>cacls \Drivers
C:\Drivers 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:\Drivers\onx>dir
Volume in drive C has no label.

Directory of C:\Drivers\onx

11/02/2011  04:17 PM                72 id.bat
03/18/2021  08:17 PM    <DIR>          Microsoft.VC90.CRT
11/02/2011  04:15 PM         1,710,592 pir.exe
2 File(s)      1,710,664 bytes



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