CVE-2026-39974: n8n-mcp has authenticated SSRF via instance-URL header in multi-tenant HTTP mode
(updated )
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.
References
- github.com/advisories/GHSA-4ggg-h7ph-26qr
- github.com/czlonkowski/n8n-mcp
- github.com/czlonkowski/n8n-mcp/commit/d9d847f230923d96e0857ccecf3a4dedcc9b0096
- github.com/czlonkowski/n8n-mcp/releases/tag/v2.47.4
- github.com/czlonkowski/n8n-mcp/security/advisories/GHSA-4ggg-h7ph-26qr
- nvd.nist.gov/vuln/detail/CVE-2026-39974
Code Behaviors & Features
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