czlonkowski n8n-mcp up to 2.47.13 getN8nApiClient/validateInstanceContext n8nApiUrl server-side request forgery

Summaryinfo

A vulnerability was found in czlonkowski n8n-mcp up to 2.47.13. It has been declared as critical. Affected is the function getN8nApiClient/validateInstanceContext. Such manipulation of the argument n8nApiUrl leads to server-side request forgery. This vulnerability is documented as CVE-2026-42449. The attack can be executed remotely. There is not any exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in czlonkowski n8n-mcp up to 2.47.13 and classified as critical. Affected by this issue is the function getN8nApiClient/validateInstanceContext. The manipulation of the argument n8nApiUrl with an unknown input leads to a server-side request forgery vulnerability. Using CWE to declare the problem leads to CWE-918. 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. Impacted is confidentiality, integrity, and availability. CVE summarizes:

n8n-MCP is an MCP server that provides AI assistants access to n8n node documentation, properties, and operations. In versions 2.47.4 through 2.47.13, the SDK embedder path (N8NDocumentationMCPServer constructor, getN8nApiClient(), and validateInstanceContext()), the synchronous URL validator in SSRFProtection.validateUrlSync() had no IPv6 checks. IPv4-mapped IPv6 addresses such as http://[::ffff:169.254.169.254] bypassed the cloud-metadata, localhost, and private-IP range checks. An attacker able to supply an n8nApiUrl value could cause the server to issue HTTP requests to cloud metadata endpoints, RFC1918 private networks, or localhost services. Response bodies are returned to the caller (non-blind SSRF), and the n8nApiKey is forwarded in the x-n8n-api-key header to the attacker-controlled target. Projects with deployments embedding n8n-mcp as an SDK using N8NDocumentationMCPServer or N8NMCPEngine with user-supplied InstanceContext are affected. The first-party HTTP server deployment was not primarily affected — it has a second async validator (validateWebhookUrl) that catches IPv6 addresses. This issue has been fixed in version 2.47.14. If users are unable to upgrade immediately as a workaround they can validate URLs before passing to the SDK, restrict egress at the network layer, and reject user-controlled n8nApiUrl values.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-42449 since 04/27/2026. The exploitation is known to be easy. The attack may be launched remotely. There are known technical details, but no exploit is available.

Upgrading to version 2.47.14 eliminates this vulnerability. Applying the patch 9639f757853149f0cb16663cc8b6b6468f27a25f is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Artificial Intelligence Software

Vendor

• czlonkowski

Name

• n8n-mcp

Version

• 2.47.0
• 2.47.1
• 2.47.2
• 2.47.3
• 2.47.4
• 2.47.5
• 2.47.6
• 2.47.7
• 2.47.8
• 2.47.9
• 2.47.10
• 2.47.11
• 2.47.12
• 2.47.13

License

• open-source

Website

• Product: https://github.com/czlonkowski/n8n-mcp/

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