Pre-Authentication Remote Code Execution in Marimo Python Notebook

CVE-2026-39987

What is CVE-2026-39987?

Marimo, a reactive Python notebook, exhibits a significant security vulnerability prior to version 0.23.0. The terminal WebSocket endpoint (/terminal/ws) allows unauthenticated access, enabling attackers to gain a complete pseudo-terminal shell and execute arbitrary commands on the host system. Unlike other WebSocket endpoints that correctly enforce authentication using validate_auth(), this specific endpoint bypasses such checks, offering a straightforward path for exploitation. This serious oversight has been addressed in the recent update, 0.23.0, which reinforces authentication measures.

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