# CVE-2026-39974: n8n-mcp authenticated SSRF via instance-URL header

Source: https://junglewise.ai/threats/cve-2026-39974-n8n-mcp-authenticated-ssrf-via-instance-url-header  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-09. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-39974 · Severity: high · CVSS 8.5 · Published 2026-04-09

n8n-mcp is a Model Context Protocol server that enables Claude to build and manage n8n workflows. An authenticated attacker with a valid bearer token can exploit a server-side request forgery vulnerability to make the server fetch arbitrary URLs—including cloud metadata endpoints, internal services, and other hosts on the network. In multi-tenant HTTP deployments where multiple operators share authentication tokens, this could expose sensitive configuration data and enable further attacks.

Technologies: [n8n-mcp (npm)](https://junglewise.ai/threats/technologies/n8n-mcp). Vendors: [npm](https://junglewise.ai/threats/vendors/npm).

## Quick answers

**Is CVE-2026-39974 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-39974 being exploited in the wild.

**How severe is CVE-2026-39974?** High severity, with a CVSS score of 8.5, published 9 April 2026.

**Which products and versions are affected?** n8n-mcp (npm) SEMVER:introduced=0,fixed=2.47.4.

**Is there a fix for CVE-2026-39974?** Yes. n8n-mcp (npm): upgrade to 2.47.4 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-39974 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-39974?** Check whether you run N8n-Mcp or n8n-mcp (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- n8n-mcp (npm): upgrade to 2.47.4 or later

  ```sh
  npm install n8n-mcp@2.47.4
  ```


## Technical details

The vulnerability is a Server-Side Request Forgery (CWE-918) in n8n-mcp's multi-tenant HTTP mode, where user-supplied URLs via the x-n8n-url and x-n8n-key headers are not sufficiently validated before being used in outbound HTTP requests. An attacker holding a valid AUTH_TOKEN can inject arbitrary URLs, causing the server to fetch and return response bodies through the JSON-RPC interface. This allows reading cloud instance metadata (AWS IMDS, GCP, Azure, Alibaba, Oracle), internal network services, and any other endpoint reachable from the server process. The vulnerability requires an authenticated caller and is specific to multi-tenant HTTP deployments; single-tenant stdio deployments and HTTP mode without multi-tenant headers are unaffected. The fix, released in version 2.47.4, adds URL validation at entry points and normalizes URLs at the API client layer.

## Affected products

- czlonkowski n8n-mcp <=2.47.3

## Identifiers

- CVE-2026-39974
- GHSA-4ggg-h7ph-26qr

## Timeline

- 2026-04-08: disclosed: Vulnerability disclosed via GHSA-4ggg-h7ph-26qr
- 2026-04-08: patched: Fix released in n8n-mcp v2.47.4

## References

- [https://github.com/czlonkowski/n8n-mcp/security/advisories/GHSA-4ggg-h7ph-26qr](https://github.com/czlonkowski/n8n-mcp/security/advisories/GHSA-4ggg-h7ph-26qr)
- [https://github.com/czlonkowski/n8n-mcp/commit/d9d847f230923d96e0857ccecf3a4dedcc9b0096](https://github.com/czlonkowski/n8n-mcp/commit/d9d847f230923d96e0857ccecf3a4dedcc9b0096)
- [https://github.com/czlonkowski/n8n-mcp](https://github.com/czlonkowski/n8n-mcp)
- [https://github.com/czlonkowski/n8n-mcp/releases/tag/v2.47.4](https://github.com/czlonkowski/n8n-mcp/releases/tag/v2.47.4)

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