A Server-Side Request Forgery vulnerability in the czlonkowski n8n-mcp SDK allows authenticated attackers to access internal cloud metadata and private network resources.

This is a Server-Side Request Forgery (CWE-918) vulnerability located in the synchronous URL validator, where a lack of IPv6 checks allows IPv4-mapped addresses to bypass security filters. The attacker must possess low privileges to supply the target URL value.

A successful exploit allows unauthorized access to internal cloud metadata endpoints, private networks, and localhost services, potentially exposing sensitive environment variables or API keys. Because the server returns response bodies and forwards the n8nApiKey header to the attacker-controlled target, critical credentials may be leaked. The high CVSS score of 8.5 reflects the severe risk of confidentiality loss across internal systems.

Immediate Action: Update the npm package n8n-mcp to version 2.47.14 or later immediately.

Proactive Monitoring: Monitor network egress logs for unexpected connections originating from the MCP server to internal metadata IPs or private address ranges.

Compensating Controls: Implement strict egress filtering at the network firewall level to block internal server requests to cloud metadata services if immediate updating is not possible.

Public Exploit Available: No

Administrators embedding n8n-mcp as an SDK should prioritize upgrading to version 2.47.14 to resolve the validation gap. Applying this patch immediately ensures that API keys and internal infrastructure remain protected from unauthorized disclosure.