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Date: Tue, 2 Mar 2021 15:46:58 -0500
From: malvuln <malvuln13@...il.com>
To: fulldisclosure@...lists.org
Subject: [FD] Backdoor.Win32.DarkKomet.irv / Insecure Permissions

Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source:
https://malvuln.com/advisory/341b2c3222122bd25c8509fc09534dec.txt
Contact: malvuln13@...il.com
Media: twitter.com/malvuln

Threat: Backdoor.Win32.DarkKomet.irv
Vulnerability: Insecure Permissions
Description: DarkKomet.irv creates an insecure hidden dir named "updter"
under c:\ drive and drops executable "updt.exe". The backdoor grants change
(C) permissions to the authenticated user group for the "updter" dir.
Standard users can rename the malware to disable it or replace with their
own executable. Then wait for a privileged user to logon to the infected
machine to potentially escalate privileges.
Type: PE32
MD5: 341b2c3222122bd25c8509fc09534dec
Vuln ID: MVID-2021-0118
Dropped files: updt.exe
Disclosure: 03/02/2021


Exploit/PoC:
gcc -c DarkKomet_Exploit.c
gcc  -o  DarkKomet_Exploit.exe  DarkKomet_Exploit.o

"DarkKomet_Exploit.c"

#include "windows.h"

void main(void){

    system("attrib -s -h C:\\updter\\updt.exe");
    system("rename  C:\\updter\\updt.exe 13");

    Sleep(1000);

    puts("[+] Disabled by renaming C:\\updter\\updt.exe to 13 ...\n");

    Sleep(1000);

    puts("[+] Backdoor.Win32.DarkKomet.irv PWNED!");
    puts("[+] MD5: 341b2c3222122bd25c8509fc09534dec");
    puts("[+] By Malvuln");
    system("pause");
}

C:\>cacls C:\updter 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 updter

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

 Directory of C:\updter

File Not Found

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

 Directory of C:\updter

06/17/2012  12:59 AM           827,392 updt.exe
               1 File(s)        827,392 bytes


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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