Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/db01783710e0c5aff92156a0e76deade.txt
Contact: malvuln13@gmail.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");
  
}


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