CVE-2026-39987

CRITICAL9.8

CISA KEV

Published 2026-04-09 · Updated 2026-06-17 · Source security-advisories@github.com

Summary

CVE-2026-39987 is a critical-severity (CVSS 9.8) vulnerability in Marimo Marimo. CISA added it to the Known Exploited Vulnerabilities catalog on April 23, 2026, which means exploitation in the wild has been confirmed; US federal agencies had to remediate it by May 7, 2026. CISA does not currently list it as used in ransomware campaigns.

All 1 known-exploited Marimo vulnerabilities →

Description

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.

CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CWE-306

CISA Known-Exploited Vulnerability

Product: Marimo — Marimo

Name: Marimo Remote Code Execution Vulnerability

Date added: 2026-04-23 · Due: 2026-05-07

Required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

References

View on NVD

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