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CVE-2026-39987

Marimo Remote Code Execution

9.8 CRITICALActively exploited (CISA KEV)Public exploitEPSS 37.9%
  1. Published9 Apr 2026
  2. Added to CISA KEV23 Apr 2026
  3. Remediation due7 May 2026
Actively exploited (CISA KEV)

Marimo contains an pre-authorization remote code execution vulnerability, allowing an unauthenticated attacked to shell access and execute arbitrary system commands.

Added to KEV: 23 Apr 2026Federal remediation due: 7 May 2026

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 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

Coreweave Marimo< 0.23.0

Remediation

Fixed in
Coreweave Marimo≥ 0.23.0

References

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Frequently asked

Is CVE-2026-39987 being actively exploited?

Yes. CVE-2026-39987 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added 23 Apr 2026.

How severe is CVE-2026-39987?

CVE-2026-39987 has a CVSS 3.1 base score of 9.8, rated critical. EPSS estimates a 37.9% probability of exploitation.

Which products are affected by CVE-2026-39987?

Affected products include Coreweave Marimo.

How do I fix CVE-2026-39987?

Upgrade affected software to a fixed version, for example Coreweave Marimo 0.23.0 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-39987 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. Because it is on the CISA KEV list, Secuno flags any affected asset as top-priority automatically. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.