🛡️ CVE-2026-39974 — n8n-mcp

🟠 CVSS 8.0 — High ✅ No Known Exploit CWE-918 OSV
8.0
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

n8n-mcp has authenticated SSRF via instance-URL header in multi-tenant HTTP mode

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

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs low-level privileges on the target. No user interaction is required. The scope is changed, meaning a successful attack can affect components beyond the vulnerable one. Rated impact: confidentiality high, integrity low, availability none.

Weakness class

CVE-2026-39974 is classified as CWE-918: Server-Side Request Forgery (SSRF). The server fetches a URL supplied by the caller, which can be pointed at internal systems it alone can reach.

Affected software

CVE-2026-39974 is recorded against 1 package.

  • n8n-mcp

Timeline and source

Published on 8 April 2026 and last revised on 17 June 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from OSV.

References

github.com (Web)
nvd.nist.gov (Advisory)
github.com (Web)
github.com (Package)
github.com (Web)

Details

Severity HIGH
CVSS Score 8.0
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N
CWE CWE-918
Public Exploit ✅ No
Source OSV
Published 2026-04-08
Updated 2026-08-12
Modified 2026-06-17

Affected Packages

Software From version Fixed in
n8n-mcp — —

Similar Threats

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