CVE-2026-39987: Marimo Remote Code Execution Vulnerability

Critical severity, CVSS 9.8. Actively exploited: in CISA KEV since 2026-04-23. EPSS: 37.9% chance of exploitation in the next 30 days.

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.

Affected products

• Coreweave Marimo: before 0.23.0 (fixed in 0.23.0)

Published 2026-04-09. Last modified 2026-06-17.