CKAN MCP Server: MQA server allowlist bypass via unanchored regex (`isValidMqaServer`)GHSA-83x6-42hr-jc76

Summary

The ckan_get_mqa_quality and ckan_get_mqa_quality_details tools restrict their server_url argument to dati.gov.it via a regular expression. The regex is anchored only at the start and places no boundary after the host, so any URL whose host merely begins with dati.gov.it — or that uses dati.gov.it as URL userinfo before an @ — passes validation while actually targeting an attacker-controlled host.

Affected code

// src/tools/quality.ts
const ALLOWED_SERVER_PATTERNS = [
  /^https?:\/\/(www\.)?dati\.gov\.it/i        // <-- no end anchor / host boundary
];
export function isValidMqaServer(serverUrl: string): boolean {
  return ALLOWED_SERVER_PATTERNS.some(pattern => pattern.test(serverUrl));
}

All of the following return true:

After passing this check, server_url flows into getMqaQuality/getMqaQualityDetails, which call makeCkanRequest(serverUrl, "package_show", { id }). The server therefore issues a request to the attacker-controlled host and returns its (parsed) response to the caller.

Impact

• The intended "dati.gov.it only" trust boundary for the MQA tools is defeated; they can be driven against arbitrary external hosts.
• The attacker host receives the request (including the dataset_id) and controls the response body that is surfaced back to the model/user — enabling response spoofing and, in an agentic setting, indirect prompt-injection content delivered under the guise of a trusted-portal tool.
• Contributes to SSRF surface: while makeCkanRequest blocks private/internal IPs, this bypass removes the domain restriction that the code intends to enforce for these tools.

The @-userinfo variant is the most severe form because validation passes on a string whose actual host is fully attacker-chosen.

Proof of concept

poc/mqa-allowlist-poc.mjs runs the verbatim regex over benign and malicious URLs:

accepted  expected_legit  url
true      true            https://dati.gov.it/opendata          <- legit
true      false           https://dati.gov.it.attacker.com/x    <- BYPASS
true      false           http://dati.gov.it.evil.example/api   <- BYPASS
true      false           https://[email protected]/x    <- BYPASS

Remediation

Validate the parsed host, not the raw string. For example:

function isValidMqaServer(serverUrl) {
  let u; try { u = new URL(serverUrl); } catch { return false; }
  if (u.protocol !== "https:") return false;
  const h = u.hostname.toLowerCase();
  return h === "dati.gov.it" || h === "www.dati.gov.it";
  // or: h === "dati.gov.it" || h.endsWith(".dati.gov.it")
}

Anchoring the regex end-to-end (/^https:\/\/(www\.)?dati\.gov\.it(\/|$)/i) also closes the suffix trick, but URL-parsing + exact host comparison is the robust fix and also neutralizes the @-userinfo variant.