Critical Pre‑Auth RCE in Marimo Notebook (CVE‑2026‑39987) Exploited Within Hours

Critical Pre‑Auth RCE in Marimo Notebook (CVE‑2026‑39987) Exploited Within Hours

What It Is — Marimo is an open‑source Python notebook platform for data‑science and interactive coding. CVE‑2026‑39987 is a pre‑authentication remote code execution flaw in the /terminal/ws WebSocket endpoint that grants an attacker a full PTY shell without any credentials.

Exploitability — The vulnerability (CVSS 9.3) was weaponized by threat actors within 10 hours of public disclosure; credential theft was completed in under 3 minutes despite the absence of a public PoC. Sysdig observed exploitation 9 hours 41 minutes after the advisory was published.

Affected Products — Marimo ≤ 0.20.4 (open‑source). The issue is patched in version 0.23.0.

TPRM Impact —

• Organizations that embed Marimo in internal analytics pipelines, SaaS products, or managed‑service offerings are exposed to immediate supply‑chain compromise.
• Successful exploitation can lead to credential theft, lateral movement, and potential exfiltration of proprietary data or intellectual property.

Recommended Actions —

• Upgrade all Marimo instances to 0.23.0 or later.
• Restrict network access to the /terminal/ws endpoint (e.g., firewall, API gateway).
• Audit logs for unexpected WebSocket connections and PTY sessions.
• Conduct a threat‑hunt for IOCs associated with the known exploit pattern.
• Review third‑party risk contracts to ensure open‑source component update obligations are enforceable.

Source: Security Affairs