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bdu:2026-05497

BREW-n8n-mcp-CVE-2026-39974 — n8n-mcp has authenticated SSRF via instance-URL header in multi-tenant HTTP mode

Affected: Homebrew: n8n-mcp

## 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 rever…

EUVD-2026-291016

fkie_cve-2026-39974

n8n-MCP is a Model Context Protocol (MCP) server that provides AI assistants with comprehensive access to n8n node documentation, properties, and operations. Prior to 2.47.4, 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. This vulnerability is fixed in 2.47.4.

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

Affected: npm: n8n-mcp

## 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.