@aborruso/ckan-mcp-server: SSRF via base_url allows access to internal networks (Potential fix bypass of CVE-2026-33060)

Summary

A known vulnerability CVE-2026-33060 indicated tools including ckan_package_search and sparql_query that accept a base_url parameter had the risk of making HTTP requests to arbitrary endpoints without restriction. A fix was applied to filter out ip addresses. However, a method to bypass exists.

Details

CKAN MCP Server validates caller-supplied CKAN server URLs by inspecting only the parsed hostname string before issuing outbound HTTP requests. In src/utils/http.ts, hostname aliases such as ip6-localhost are not equal to localhost, are not dotted IPv4 literals, and are not bracketed IPv6 literals, so they pass the SSRF filter but can resolve to loopback when the server performs the request. A remote MCP caller that can invoke CKAN tools with a server_url can therefore make the server connect to local or private addresses and, for CKAN-shaped responses, receive response-derived data.

Fix

Replaced the single hostname === 'localhost' check with a blocked-hostname Set covering ip6-localhost and ip6-loopback. Patched in commit c761045a1b7c5f40d2626540dd2ef1d4feb91f8c.

@aborruso/ckan-mcp-server thanks hibrian827 for responsibly disclosing this issue.