CVE-2026-39987 PoC — marimo Affected by Pre-Auth Remote Code Execution via Terminal WebSocket Authentication Bypass

Title:marimo Affected by Pre-Auth Remote Code Execution via Terminal WebSocket Authentication Bypass (CVE-2026-39987)
Description:marimo is a reactive Python notebook. Prior to 0.23.0, Marimo has a Pre-Auth RCE vulnerability. The terminal WebSocket endpoint /terminal/ws lacks authentication validation, allowing an unauthenticated attacker to obtain a full PTY shell and execute arbitrary system commands. Unlike other WebSocket endpoints (e.g., /ws) that correctly call validate_auth() for authentication, the /terminal/ws endpoint only checks the running mode and platform support before accepting connections, completely skipping authentication verification. This vulnerability is fixed in 0.23.0.

Marimo versions <= 0.20.4 contain an unauthenticated remote code execution vulnerability. The terminal WebSocket endpoint /terminal/ws lacks authentication validation, allowing an unauthenticated attacker to connect via WebSocket, obtain a full PTY shell, and execute arbitrary OS commands on the underlying server.

 id: CVE-2026-39987

info:
  name: Marimo <= 0.20.4 - Pre-Auth Terminal WebSocket RCE
  author: ritik

...