An unauthenticated attacker can connect to marimo’s terminal WebSocket endpoint, gain a full PTY shell, and run arbitrary system commands, compromising confidentiality, integrity, and availability of the host. The weakness is a missing authentication check (CWE‑306) that allows exploitation without valid credentials.

marimo versions prior to 0.23.0 are affected; any instance of the marimo-team:marimo product before this release is vulnerable.

The CVSS score of 9.3 indicates critical severity. Because the endpoint accepts connections over an open WebSocket without authentication, a remote attacker can exploit this directly over the network, likely from anywhere that can reach the service. The EPSS score of 58% indicates a high probability of exploitation. The vulnerability is listed in the CISA KEV catalog. The risk is therefore high due to the critical severity and the ease of remote exploitation.