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MEDIUM5.3

GHSA-83x6-42hr-jc76

CKAN MCP Server: MQA server allowlist bypass via unanchored regex (`isValidMqaServer`)

Quick fix

GHSA-83x6-42hr-jc76 — @aborruso/ckan-mcp-server: upgrade to the fixed version with the command below.

npm install @aborruso/ckan-mcp-server@0.4.112

Details

## 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

```js // 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`:

| URL | Real host | |-----|-----------| | `https://dati.gov.it.attacker.com/x` | `dati.gov.it.attacker.com` (attacker) | | `http://dati.gov.it.evil.example/api` | `dati.gov.it.evil.example` (attacker) | | `https://dati.gov.it@attacker.com/x` | `attacker.com` (userinfo trick) |

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://dati.gov.it@attacker.com/x <- BYPASS ```

## Remediation

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

```js 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.

Are you affected?

Enter the version of the package you're using.

Affected packages

npm/@aborruso/ckan-mcp-server
Introduced in: 0Fixed in: 0.4.112
Fixnpm install @aborruso/ckan-mcp-server@0.4.112

References