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CVE-2026-39987

Coreweave Marimo•CRITICAL · CVSS 9.8• In the wild In CISA KEV

What is CVE-2026-39987?

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.

CVSS9.8 NVD 3.1

SeverityCRITICAL

Exploitation In the wild In CISA KEV

EPSS38% · P99

Triage statusActive Exploit

ActionPatch immediately

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

CWECWE-306

NVD published2026-04-09

NVD last modified2026-06-17

Timeline

2026-04-09Published to the U.S. National Vulnerability Database (NVD)
2026-04-11First covered in a defend.network daily briefing
2026-04-23Added to the CISA Known Exploited Vulnerabilities (KEV) catalog
2026-05-07CISA federal remediation deadline (BOD 22-01)
2026-06-17NVD record last updated

CISA Known Exploited Vulnerability

Marimo Remote Code Execution Vulnerability

Added to KEV2026-04-23

Federal patch deadline2026-05-07

Known ransomware useUnknown

Affected product

Coreweave Marimo

Remediation Steps

Apply the vendor patch for Marimo immediately
Audit internet-exposed Marimo notebook instances and restrict access to trusted networks
Review access logs for unauthorized changes to notebooks or credential extraction
Rotate all cloud credentials and API keys stored in or accessible via Marimo instances
Implement network segmentation to isolate notebook environments from sensitive systems

References

Referenced in our briefings & reports

Vulnerability Priority Report – Week 1 of June 2026 (June 1 – 7)
Vulnerability Priority Report – Week 2 of April 2026 (April 13 – 19)
ChatGPT malware abuse, Marimo CVE-2026-39987 LLM exploitation, Russian infrastructure arrests (2026-05-30)
Iran PLC attacks; Marimo RCE exploited in 10h; GlassWorm IDE infection (2026-04-12)
Marimo RCE exploited; Iran targets 4,000 US PLCs; Russian token theft (2026-04-11)

Related vulnerabilities

CVE-2026-76480 (same weakness: CWE-306)
CVE-2026-85889 – Microsoft Azure Ai Foundry (same weakness: CWE-306)
CVE-2026-67277 – MikroTik RouterOS (same weakness: CWE-306)
CVE-2026-76640 (same weakness: CWE-306)
CVE-2026-72529 – TrueConf Server (same weakness: CWE-306)
CVE-2026-56164 – Microsoft SharePoint Server (same weakness: CWE-306)

Browse all tracked CVEs in the defend.network CVE database →

🤖 This CVE page is generated by defend.network from NVD, CISA KEV, EPSS, and our verified daily briefings. Severity and exploitation data come from official sources; always verify remediation steps against the official vendor advisory before acting in production.