CVE-2026-39987

Q: How do I fix CVE-2026-39987?

Upgrade marimo to 0.23.0 or later.

Q: Is CVE-2026-39987 being actively exploited?

Yes. CVE-2026-39987 is listed in the CISA Known Exploited Vulnerabilities catalog, which means exploitation has been observed in the wild. US federal agencies were required to remediate it by 2026-05-07. Treat it as a priority whatever its CVSS score says.

Q: How severe is CVE-2026-39987?

CVE-2026-39987 has a CVSS v3 base score of 9.8, rated critical. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.

Q: What does CVE-2026-39987 affect?

Published advisories record a fix for marimo (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.

CRITICALCISA KEVEPSS 100th pctl

9.8

CVSS v3

NVD

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.

CWE-306Missing Authentication for Critical Function

How to fix

Remediation Available

marimoNVD

Affected:< 0.23.0Fixed in:0.23.0CVE-2026-39987derived from NVD

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

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

Exploit Intelligence

96.58%probability of exploitation in 30 days

100thpercentile

Very high risk: more likely to be exploited than 100% of all known CVEs.

Known Exploited Vulnerability (CISA KEV)

Remediation due: 2026-05-07

References

Patch2

Exploit2

Government Resource1

cisa.gov

Related Vulnerabilities

Other CWE-306 (Missing Authentication for Critical Function) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2025-3248	Critical	9.8	100%	KEV + Ransom	Fix
CVE-2017-10271	High	7.5	100%	KEV + Ransom	-
CVE-2023-42793	Critical	9.8	100%	KEV + Ransom	Fix
CVE-2022-1388	Critical	9.8	100%	KEV + Ransom	Fix
CVE-2026-33017	Critical	9.8	100%	KEV	Fix
CVE-2021-37415	Critical	9.8	100%	KEV	-

Common questions

How do I fix CVE-2026-39987?

Upgrade marimo to 0.23.0 or later.

Is CVE-2026-39987 being actively exploited?

Yes. CVE-2026-39987 is listed in the CISA Known Exploited Vulnerabilities catalog, which means exploitation has been observed in the wild. US federal agencies were required to remediate it by 2026-05-07. Treat it as a priority whatever its CVSS score says.

How severe is CVE-2026-39987?

CVE-2026-39987 has a CVSS v3 base score of 9.8, rated critical. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.

What does CVE-2026-39987 affect?

Published advisories record a fix for marimo (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-04-23.