SSRF in @aborruso/ckan-mcp-server via base_url allows access to internal networks

Summary

The @aborruso/ckan-mcp-server MCP server provides tools including ckan_package_search and sparql_query that accept a base_url parameter, making HTTP requests to arbitrary endpoints without restriction. A CKAN portal client has no legitimate reason to contact cloud metadata or internal network services.

Severity

Attack complexity is HIGH because exploitation requires prompt injection via malicious content (webpage, document) while the victim's AI assistant has this MCP server connected.

Proof of Concept

Tested inside Docker-in-Docker isolated environment with canary HTTP sidecar.

{"tool": "ckan_package_search", "arguments": {"base_url": "http://canary:8080/ssrf", "query": "test"}}

Result: Canary received 9 HTTP requests. The high request volume confirms no rate limiting or URL validation.

Root Cause

No URL validation on base_url parameter. No private IP blocking (RFC 1918, link-local 169.254.x.x), no cloud metadata blocking. The sparql_query and ckan_datastore_search_sql tools also accept arbitrary base URLs and expose injection surfaces.

Impact

Internal network scanning, cloud metadata theft (IAM credentials via IMDS at 169.254.169.254), potential SQL/SPARQL injection via unsanitized query parameters. Attack requires prompt injection to control the base_url parameter.

Recommended Fix

1. Validate base_url against a configurable allowlist of permitted CKAN portals
2. Block private IP ranges (RFC 1918, link-local)
3. Block cloud metadata endpoints (169.254.169.254)
4. Sanitize SQL input for datastore queries
5. SPARQL endpoint allowlist

Credit

Discovered by Andrei Boldyrev of Munio Security Research using munio