CVE-2026-39987: Marimo Remote Code Execution Vulnerability

Should you act?

Exploited: patch now if you run it

CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• 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.

From the GitHub advisory

Summary

Marimo (19.6k stars) 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.

Affected Versions

Marimo

CISA’s summary

Marimo contains an pre-authorization remote code execution vulnerability, allowing an unauthenticated attacked to shell access and execute arbitrary system commands.

Weakness type: CWE-306.

Product: Marimo Marimo · Assigned by: GitHub_M · Published: 2026-04-09

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Attack requirements: none
• Privileges required: none (no login)
• User interaction: none

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• 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.

Timeline

• 2026-04-08 — GitHub-reviewed advisory GHSA-2679-6mx9-h9xc published (critical)
• 2026-04-09 — CVE record published by GitHub_M
• 2026-04-23 — Added to CISA’s Known Exploited Vulnerabilities catalog
• 2026-04-24 — CVE record last updated
• 2026-05-07 — CISA remediation deadline for US federal agencies

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vendor and project advisories, patches

1. Listed in CISA KEV notes (github.com) github.com

Vulnerability records

1. GitHub Advisory GHSA-2679-6mx9-h9xc github.com
2. CVE.org record CVE-2026-39987 cve.org
3. NVD entry CVE-2026-39987 nvd.nist.gov

Government

1. CISA Known Exploited Vulnerabilities catalog entry cisa.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. sysdig.com sysdig.com
4. cisa.gov cisa.gov

All exploited Marimo vulnerabilities · Critical PyPI advisories · Today’s Security Digest