---
title: "CVE-2026-39987: Marimo Remote Code Execution Vulnerability"
url: https://erroneo.us/security/cve/CVE-2026-39987/
description: "CVE-2026-39987 (Marimo Marimo): Exploited in the wild (CISA KEV). marimo is a reactive Python notebook. Prior to 0.23.0, Marimo has a Pre-Auth RCE…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-04-09
date_modified: 2026-04-27
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-39987"
kev: true
cvss: 9.3
epss: 0.37865
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-39987: Marimo Remote Code Execution Vulnerability

**Signal:** Exploited: patch now if you run it. CISA has confirmed exploitation in the wild. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Yes, if you run Marimo Marimo. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2026-04-23, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2026-05-07 ; treat that as the outer limit, not the target.
- EPSS 37.9% , percentile 99: FIRST’s model estimates a 37.9% chance of exploitation activity in the next 30 days, higher than 99% of all scored CVEs (very high). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes marimo (PyPI) < 0.23.0, fixed in 0.23.0 . Check your lockfile, including transitive dependencies.

## What it is

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 validateauth() 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.

## Affected packages

- PyPI `marimo` < 0.23.0 → fixed: 0.23.0

## Affected products (CVE record)

- marimo-team marimo: < 0.23.0

## Severity

- GitHub_M CVSS 4.0: 9.3 `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`
- GitHub CVSS 4.0: 9.3 `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`

## Exploitation

- CISA KEV: added 2026-04-23; federal due date 2026-05-07. Known ransomware use: Unknown.
- 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 SSVC assessment: exploitation active , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 37.87% probability of exploitation activity in the next 30 days; percentile 99.

## Sources

- [Listed in CISA KEV notes (github.com)](https://github.com/marimo-team/marimo/security/advisories/GHSA-2679-6mx9-h9xc)
- [GitHub Advisory GHSA-2679-6mx9-h9xc](https://github.com/advisories/GHSA-2679-6mx9-h9xc)
- [CVE.org record CVE-2026-39987](https://www.cve.org/CVERecord?id=CVE-2026-39987)
- [NVD entry CVE-2026-39987](https://nvd.nist.gov/vuln/detail/CVE-2026-39987)
- [CISA Known Exploited Vulnerabilities catalog entry](https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-39987)
- [github.com](https://github.com/marimo-team/marimo/pull/9098)
- [github.com](https://github.com/marimo-team/marimo/commit/c24d4806398f30be6b12acd6c60d1d7c68cfd12a)
- [sysdig.com](https://www.sysdig.com/blog/marimo-oss-python-notebook-rce-from-disclosure-to-exploitation-in-under-10-hours)
- [cisa.gov](https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-39987)

---
Source page: https://erroneo.us/security/cve/CVE-2026-39987/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt