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Authenticated SSRF via instance-URL header in multi-tenant HTTP mode

High
czlonkowski published GHSA-4ggg-h7ph-26qr Apr 8, 2026

Package

npm n8n-mcp (npm)

Affected versions

<=2.47.3

Patched versions

>=2.47.4

Description

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

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
Low
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N

CVE ID

CVE-2026-39974

Weaknesses

Server-Side Request Forgery (SSRF)

The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination. Learn more on MITRE.

Credits