feat: default BIND_HOST to loopback so the dashboard is not LAN-exposed

.env.example

@@ -1,4 +1,7 @@
 PORT=5555
+# Listen address. Loopback by default (the dashboard exposes SSH + power controls);
+# set to the host LAN IP or 0.0.0.0 to allow access from another machine.
+BIND_HOST=127.0.0.1
 LLM_PORT=8888
 POLL_INTERVAL_GPU=2000
 POLL_INTERVAL_CPU=2000

CHANGELOG.md

@@ -7,6 +7,13 @@ Format: version sections are listed newest first.
 
 ---
 
+## [Unreleased]
+
+### Security
+- **`BIND_HOST` now defaults to `127.0.0.1` (loopback) instead of `0.0.0.0`** — the dashboard is unauthenticated and can SSH into and power off Sparks, so it is no longer reachable on the LAN by default. Set `BIND_HOST` to the host's LAN IP (or `0.0.0.0`) to opt in to remote access. **Migration:** if you access sparkDash from another machine via bare-metal `npm start`, set `BIND_HOST` explicitly. Docker is unaffected — `docker-compose.yml` already sets `BIND_HOST=0.0.0.0`. Startup now also warns when bound to a non-loopback address.
+
+---
+
 ## [1.4.7] — 2026-08-02
 
 ### Added

README.md

@@ -228,7 +228,7 @@ Copy `.env.example` to `.env` if needed:
 
 | Variable | Default | Description |
 |----------|---------|-------------|
-| `BIND_HOST` | `0.0.0.0` | HTTP and WebSocket listen address |
+| `BIND_HOST` | `127.0.0.1` | HTTP and WebSocket listen address. Loopback by default — the dashboard exposes SSH + power controls, so set a LAN IP (or `0.0.0.0`) to allow remote access. |
 | `PORT` | `5555` | HTTP + WebSocket listen port |
 | `LLM_PORT` | `8888` | Default LLM probe port |
 | `POLL_INTERVAL_GPU` | `2000` | GPU poll (ms) |
@@ -243,8 +243,11 @@ Copy `.env.example` to `.env` if needed:
 | `HOST_SYS_PATH` | `/host/sys` | Host sys mount |
 | `HOST_ROOT_PATH` | `/host/root` | Host root mount |
 
-> When using Docker's default bridge network, keep `BIND_HOST=0.0.0.0`.  
-> With `network_mode: host`, use `BIND_HOST=127.0.0.1` to restrict access to the local host or a reverse proxy.
+> The listener defaults to `127.0.0.1` (loopback) so the dashboard — which can SSH into and
+> power off your Sparks — isn't reachable on the LAN by default. Set `BIND_HOST` to the host's
+> LAN IP (or `0.0.0.0`) to reach it from another machine. The provided `docker-compose.yml`
+> (`network_mode: host`) sets `BIND_HOST=0.0.0.0` explicitly; restrict access at the network
+> layer, or set `127.0.0.1` when running behind a reverse proxy.
 
 ### Adding a Spark
 

server/index.js

@@ -25,7 +25,10 @@ const __filename = fileURLToPath(import.meta.url);
 const __dirname = path.dirname(__filename);
 const ROOT = path.resolve(__dirname, "..");
 
-const BIND_HOST = process.env.BIND_HOST || "0.0.0.0";
+// Default to loopback: the dashboard exposes SSH and remote power controls, so it
+// should not be reachable on the LAN unless explicitly opted in. Set BIND_HOST to the
+// host's LAN IP (or 0.0.0.0) to expose it; the provided docker-compose.yml sets it.
+const BIND_HOST = process.env.BIND_HOST || "127.0.0.1";
 const PORT = parseInt(process.env.PORT || "5555", 10);
 const LLM_PORT = parseInt(process.env.LLM_PORT || "8888", 10);
 
@@ -1164,6 +1167,13 @@ startBroadcast();
 server.listen(PORT, BIND_HOST, () => {
   console.log(`[sparkDash] server listening on http://${BIND_HOST}:${PORT}`);
   console.log(`[sparkDash] WebSocket endpoint ws://${BIND_HOST}:${PORT}/ws`);
+  const isLoopback =
+    BIND_HOST === "localhost" || BIND_HOST === "::1" || /^127\./.test(BIND_HOST);
+  if (isLoopback) {
+    console.log(`[sparkDash] localhost-only; set BIND_HOST=<lan-ip> (or 0.0.0.0) to allow remote access`);
+  } else {
+    console.warn(`[sparkDash] WARNING: bound to ${BIND_HOST} — reachable on the LAN. This dashboard is unauthenticated and can SSH into and power off your Sparks; restrict access at the network/firewall layer.`);
+  }
   startAllMonitors();
 });