full-disclosure - [FD] Trojan-Dropper.Win32.Demp.rft / Insecure Permissions

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Date: Sat, 20 Mar 2021 21:47:13 -0400
From: malvuln <malvuln13@...il.com>
To: fulldisclosure@...lists.org
Subject: [FD] Trojan-Dropper.Win32.Demp.rft / Insecure Permissions

Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source:
https://malvuln.com/advisory/db01783710e0c5aff92156a0e76deade.txt
Contact: malvuln13@...il.com
Media: twitter.com/malvuln

Threat: Trojan-Dropper.Win32.Demp.rft
Vulnerability: Insecure Permissions
Description: The specimen creates a dir named "tmp" under c:\ drive and
grants change (C) permissions to the authenticated user group. Standard
users can rename the "DaumCleans.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: db01783710e0c5aff92156a0e76deade
Vuln ID: MVID-2021-0138
Dropped files: DaumCleans.exe
Disclosure: 3/20/2021

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

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

 Directory of C:\tmp

03/20/2021  09:27 PM            38,824 DaumCleans.exe
               1 File(s)         38,824 bytes

#include "windows.h"

void main(void){

    system("rename  C:\\tmp\\DaumCleans.exe 13");

    puts("[+] Disabled by renaming C:\\tmp\\DaumCleans.exe to 13 ...");
    puts("[+] Reboot your machine");

    Sleep(1000);

    puts("[+] Trojan-Dropper.Win32.Demp.rft PWNED!");
    puts("[+] MD5: db01783710e0c5aff92156a0e76deade");
    puts("[+] By Malvuln");
    system("pause");

}

Disclaimer: The information contained within this advisory is supplied
"as-is" with no warranties or guarantees of fitness of use or otherwise.
Permission is hereby granted for the redistribution of this advisory,
provided that it is not altered except by reformatting it, and that due
credit is given. Permission is explicitly given for insertion in
vulnerability databases and similar, provided that due credit is given to
the author. The author is not responsible for any misuse of the information
contained herein and accepts no responsibility for any damage caused by the
use or misuse of this information. The author prohibits any malicious use
of security related information or exploits by the author or elsewhere. Do
not attempt to download Malware samples. The author of this website takes
no responsibility for any kind of damages occurring from improper Malware
handling or the downloading of ANY Malware mentioned on this website or
elsewhere. All content Copyright (c) Malvuln.com (TM).

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