CVE-2026-39987

Marimo is a reactive Python notebook application that contains a critical pre-authentication remote code execution vulnerability in versions prior to 0.23.0. The terminal WebSocket endpoint /terminal/ws fails to properly validate user authentication, allowing unauthenticated attackers to establish connections and obtain shell access. This vulnerability affects the core functionality of the marimo application, impacting any deployment where the affected versions are in use. The vulnerability has a high FAUCET Risk Score of 87.0/100 and presents a severe threat due to its unauthenticated attack vector and minimal complexity requirements. An attacker can exploit this flaw without any credentials or authentication tokens, directly connecting to the terminal endpoint to execute arbitrary system commands with the privileges of the marimo process. The lack of authentication checks means any network-accessible marimo instance running an affected version is immediately exploitable. The vulnerability is actively being exploited in the wild and has been designated for inclusion on the Known Exploited Vulnerabilities (KEV) catalog, indicating confirmed real-world exploitation activity. This high-visibility status combined with the straightforward nature of the attack makes prompt patching to version 0.23.0 or later a critical priority for all marimo users and organizations operating this software.