CVE-2026-39987: Marimo Remote Code Execution Vulnerability

In short

Marimo Marimo has a weakness classified as missing authentication for critical function (CWE-306). CISA added it to its Known Exploited Vulnerabilities catalog on 2026-04-23. NVD lists CVSS 4.0 at 9.3 CRITICAL.

What it is

“Marimo contains an pre-authorization remote code execution vulnerability, allowing an unauthenticated attacked to shell access and execute arbitrary system commands.” — CISA KEV, retrieved 2026-11-01

“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.” — NVD, retrieved 2026-11-01

Who is affected

Marimo Marimo. NVD lists the following versions as affected:

• Versions before 0.23.0

Exploitation status

CISA KEV added: 2026-04-23. Known ransomware campaign use: Not reported by CISA. Due date CISA set for US federal civilian agencies: 2026-05-07.

Scores

NVD CVSS 4.0: 9.3 CRITICAL; vector 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X; source [email protected].

EPSS by FIRST: 99.56%; percentile 99.95; score date 2026-10-31. EPSS estimates the probability of exploitation in the next 30 days.

CWE: CWE-306.

Timeline

CISA 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.” — CISA KEV

What to do

• Confirm whether you run Marimo Marimo and which version.
• Apply the vendor update or mitigation in the advisory.
• Follow CISA’s required action.
• Review the vendor guidance on signs of compromise.
• Track the fix through completion.

References

• Patch: https://github.com/marimo-team/marimo/commit/c24d4806398f30be6b12acd6c60d1d7c68cfd12a
• Issue Tracking, Patch: https://github.com/marimo-team/marimo/pull/9098
• NVD detail
• CVE.org record
• CISA KEV catalog

Sources and dates

CISA Known Exploited Vulnerabilities Catalog, version 2026.10.30; retrieved 2026-11-01. CISA KEV data: CC0 1.0. No endorsement by CISA.

NVD retrieved: 2026-11-01. This product uses the NVD API but is not endorsed or certified by the NVD.

EPSS scores by FIRST; score date 2026-10-31.