FIX CARD
PRODUCT Langfuse
SEVERITY MEDIUM
Langfuse reachable from the internet
Why it matters
Your LLM observability stack is publicly reachable — Langfuse stores prompts, completions, tool calls, and agent session state that can contain customer data and secrets. If the sign-up page is open, anyone can create an account and start reading those traces.
Fix it: 3 steps
- Disable public sign-up: set NEXT_PUBLIC_SIGN_UP_DISABLED=true (Langfuse v3) and restart; create accounts by invitation only.
- Don't expose it on a public IP: bind to 127.0.0.1 or your VPN interface and put an authenticating reverse proxy or VPN in front.
- Block the port at the firewall:
sudo ufw deny 3000.
Verify it’s fixed
curl -m 5 http://YOUR_SERVER_IP:3000/auth/sign-up # should time out or 404/redirect to login, not render a sign-up form
References
Not sure if your stack is exposed?
Run the free check: usually under a minute, safe read-only probes.
Scan your stack