GHSA-cmrh-wvq6-wm9r n8n-mcp webhook and API client paths has an authenticated SSRF

• npm n8n-mcp: >= 2.18.7, < 2.50.2 → fixed in 2.50.2

Summary Authenticated Server-Side Request Forgery affecting the webhook trigger tools, the n8n API client (`N8N_API_URL`), and per-request URLs supplied via the `x-n8n-url` header in multi-tenant HTTP mode. Impact A caller with access to the MCP session can drive HTTP requests from the n8n-mcp host to internal services and cloud metadata endpoints that the SSRF gate is meant to block. The response body is returned to the caller, making internal-service enumeration and credential theft immediate without any out-of-band channel. • Multi-tenant HTTP deployments where tenants share an `AUTH_TOKEN`: any tenant with valid credentials can reach the operator's cloud metadata service and exfiltrate temporary IAM / GCP service account / Azure managed-identity credentials. • Single-tenant deployments: indirect prompt injection through tool arguments reaches the same surface; an attacker who can influence the LLM's tool calls can read internal services from the n8n-mcp host. • Stdio deployments are reachable via the same prompt-injection path. Patched Versions Fixed in `[email protected]`. Note for operators: The same SSRF gate that previously covered webhook URLs now also covers the n8n API client base URL. If `N8N_API_URL` points at `http://localhost:5678` (n8n on the same host) or an RFC1918 address (n8n on the same private network), set `WEBHOOK_SECURITY_MODE=moderate` (allows localhost, still blocks RFC1918 and cloud metadata) or `WEBHOOK_SECURITY_MODE=permissive` (allows RFC1918 too — only safe on a trusted private network). Default `strict` is correct for deployments where n8n is reachable at a public hostname. Workarounds For deployments that cannot upgrade immediately: 1. Restrict network egress from the n8n-mcp host with a firewall, reverse proxy, or cloud security group. Explicitly deny cloud metadata IPs (`169.254.169.254`, `169.254.170.2`, `100.100.100.200`, `192.0.0.192`, and the GCP `metadata.google.internal` resolved IP) and any RFC1918 networks the server does not legitimately need to reach. 2. Run in stdio mode instead of HTTP if the multi-tenant surface is not needed (no shared `AUTH_TOKEN` to compromise). 3. Disable workflow management tools via `DISABLED_TOOLS=n8n_trigger_webhook_workflow,n8n_create_workflow,n8n_test_workflow` if the deployment does not need them. Credit Reported by @fg0x0.