GHSA-4ggg-h7ph-26qr n8n-mcp has authenticated SSRF via instance-URL header in multi-tenant HTTP mode

• npm n8n-mcp: < 2.47.4 → fixed in 2.47.4

Impact An authenticated Server-Side Request Forgery in `n8n-mcp` allows a caller holding a valid `AUTH_TOKEN` to cause the server to issue HTTP requests to arbitrary URLs supplied through multi-tenant HTTP headers. Response bodies are reflected back through JSON-RPC, so an attacker can read the contents of any URL the server can reach — including cloud instance metadata endpoints (AWS IMDS, GCP, Azure, Alibaba, Oracle), internal network services, and any other host the server process has network access to. The primary at-risk deployments are multi-tenant HTTP installations where more than one operator can present a valid `AUTH_TOKEN`, or where a token is shared with less-trusted clients. Single-tenant stdio deployments and HTTP deployments without multi-tenant headers are not affected. Affected versions `n8n-mcp` ≤ `2.47.3` (all versions up to and including 2.47.3). Patched versions `n8n-mcp` `2.47.4` and later. Workarounds If you cannot immediately upgrade: 1. Egress filtering at the network layer — block outbound traffic from the `n8n-mcp` container to RFC1918 ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16), link-local `169.254.0.0/16`, and any other internal ranges. This defends against any future SSRF-class issue and is recommended even after upgrading. 2. Disable multi-tenant headers — if your deployment does not require per-request instance switching, unset `ENABLE_MULTI_TENANT` and do not accept `x-n8n-url` / `x-n8n-key` headers at the reverse proxy. 3. Restrict `AUTH_TOKEN` distribution — ensure the bearer token is only held by fully trusted operators until you can upgrade. Remediation Upgrade to `n8n-mcp` 2.47.4 or later. No configuration changes are required; the fix adds validation at the URL entry points and normalizes URLs at the API client layer. Credits Reported by the Eresus Security Research Team. @ibrahmsql