CVE-2026-39987

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.

Severity scores

Each score is shown as its source gave it. They are not averaged or merged.

• 9.3CVSS 4.0, Criticalfrom the CNA (GitHub_M)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

What to do

• Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.CISA KEV required action

Historical context and remediation

This reference retains the original CVE publication date. A recent record update does not mean a new attack occurred.

No separately sourced impact summary is available on this page yet. Consult the description, version data and dated exploitation evidence.

Version statuses below come from the CNA. An “unaffected” version is not necessarily a currently supported release or proof of a patch date. EPSS is a dated risk estimate, not a count of historical attacks.

Read the original CVE record.

Affected products

Timeline

1. 9 Apr 2026 Published
2. 23 Apr 2026 CVE-2026-39987 added to CISA KEV
3. 23 Apr 2026 Added to the CISA KEV catalogue

Weakness

• CWE-306

References

• https://github.com/marimo-team/marimo/security/advisories/GHSA-2679-6mx9-h9xcx_refsource_CONFIRM
• https://github.com/marimo-team/marimo/pull/9098x_refsource_MISC
• https://github.com/marimo-team/marimo/commit/c24d4806398f30be6b12acd6c60d1d7c68cfd12ax_refsource_MISC