CVE-2026-39987

Name: CVE-2026-39987
Creator: NVD / NIST
Published: 2026-04-09T18:17:02.807+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.3/10Actively ExploitedEPSS 95.64%

Last modified Jun 17, 2026

CVE-2026-39987 is a critical-severity vulnerability rated 9.3/10 on the CVSS scale. marimo is a reactive Python notebook. Prior to 0.23.0, Marimo has a Pre-Auth RCE vulnerability. CISA has confirmed active exploitation in the wild. EPSS estimates a 95.64% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

9.8/10

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

CVSS 4.0

9.3/10

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS Probability

95.64%

99.9th percentile

Probability of exploitation in the next 30 days. Learn more

Exploitation Status

This vulnerability is listed in CISA’s Known Exploited Vulnerabilities catalog, confirming active exploitation in the wild. Federal agencies must remediate by May 7, 2026.

Weakness Enumeration

CWE-306

Affected Software

Vendor	Product	Versions
Coreweave	Marimo	< 0.23.0

References

https://github.com/marimo-team/marimo/commit/c24d4806398f30be6b12acd6c60d1d7c68cfd12aPatch
https://github.com/marimo-team/marimo/pull/9098Issue Tracking, Patch
https://github.com/marimo-team/marimo/security/advisories/GHSA-2679-6mx9-h9xcExploit, Mitigation, Vendor Advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-39987US Government Resource
https://www.sysdig.com/blog/marimo-oss-python-notebook-rce-from-disclosure-to-exploitation-in-under-10-hoursExploit, Third Party Advisory

Timeline

Published: Apr 9, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-39987?

How severe is CVE-2026-39987?

CVE-2026-39987 has a CVSS score of 9.3/10 (CRITICAL severity). The EPSS model estimates a 95.64% probability of exploitation in the next 30 days. This vulnerability is listed in CISA's Known Exploited Vulnerabilities catalog.

How do I fix CVE-2026-39987?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-39987?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST