What is CVE-2026-39987?

CVE-2026-39987 is a critical-severity vulnerability in Coreweave Marimo, classified under Missing Authentication for Critical Function. CVSS score: 9.8/10. Published 2026-04-09.

How severe is CVE-2026-39987?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Is CVE-2026-39987 known to be exploited?

Yes. CVE-2026-39987 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2026-04-23), indicating it is being actively exploited. 12 public proof-of-concept repositories are indexed.

Auth bypass in Coreweave Marimo

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 a…

Vulnerability class: Broken Authentication

EPSS: 0.956 (99.9th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

Affected products

Coreweave Marimo
Marimo-team Marimo — versions < 0.23.0

Weakness classification (CWE)

CWE-306 — Missing Authentication for Critical Function

CISA KEV (Known Exploited Vulnerabilities)

This CVE is on the CISA KEV catalog, added on 2026-04-23. CISA KEV inclusion means CISA has confirmed in-the-wild exploitation; US federal agencies are required to remediate within a published due date.

BOD 22-01 due date: 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.

Public proof-of-concept exploits

References

security-advisories@github.com (x_refsource_CONFIRM, Exploit, Mitigation, Vendor Advisory)
security-advisories@github.com (Patch, x_refsource_MISC, Issue Tracking)
security-advisories@github.com (Patch, x_refsource_MISC)
134c704f-9b21-4f2e-91b3-4a467353bcc0 (US Government Resource)
134c704f-9b21-4f2e-91b3-4a467353bcc0 (Exploit, Third Party Advisory)

Frequently asked questions

What is CVE-2026-39987?: CVE-2026-39987 is a critical-severity vulnerability in Coreweave Marimo, classified under Missing Authentication for Critical Function. CVSS score: 9.8/10. Published 2026-04-09.
How severe is CVE-2026-39987?: Critical severity. CVSS v3 base score is 9.8 out of 10.
Is CVE-2026-39987 known to be exploited?: Yes. CVE-2026-39987 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2026-04-23), indicating it is being actively exploited. 12 public proof-of-concept repositories are indexed.