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Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 7 May 2026.
MarimoApplication · Coreweave

CVE-2026-39987

CRITICAL · 9.8 CVSS v3.1 Published 2026-04-09
Fix available
A fix is available. Upgrade to 0.23.0 or later.
See remediation →
100/100
Remediation priority · Urgent
In the wild High EPSS Public exploit Remotely reachable No privileges Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The marimo notebook application has a Pre-Auth RCE vulnerability in the terminal WebSocket endpoint /terminal/ws. This endpoint skips the validate_auth() check that other WebSocket endpoints (like /ws) properly perform, allowing unauthenticated attackers to obtain a full PTY shell and execute arbitrary system commands. The vulnerability is caused by the endpoint only checking running mode and platform support before accepting connections.

MitigationUpgrade to marimo version 0.23.0 or later which includes the authentication validation fix. If immediate upgrade is not possible, consider network-level restrictions on the /terminal/ws endpoint.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
MarimoApplication
Affected:< 0.23.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify marimo version
    Run 'pip show marimo' or 'pip list | grep marimo' to retrieve the installed version number
    Affected if The version displayed is lower than 0.23.0 (e.g., 0.22.0, 0.21.0, etc.)
  2. Locate marimo server configuration
    Check if marimo is being run as a server - look for startup scripts, Docker files, or process listings that invoke 'marimo run' or 'marimo server'
    Affected if Marimo is running as a web server and the terminal WebSocket endpoint is exposed to network access
  3. Test terminal WebSocket endpoint accessibility
    Attempt to access the /terminal/ws endpoint via WebSocket connection (e.g., using wscat or similar tool) without providing any authentication credentials
    Affected if The WebSocket connection to /terminal/ws establishes successfully without requiring authentication
  4. Inspect server logs for terminal endpoint activity
    Review marimo server logs for any requests to /terminal/ws endpoints, particularly unauthenticated ones
    Affected if Logs show unauthenticated access to /terminal/ws or the endpoint is reachable without auth tokens
  5. Check network exposure
    Determine if the marimo server is bound to a publicly accessible IP or exposed via port forwarding, VPN, or firewall rules
    Affected if The server is accessible from untrusted networks and version is below 0.23.0

You are affected if marimo version is below 0.23.0 AND the /terminal/ws WebSocket endpoint is accessible without authentication on your server.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 0.23.0 or later
Fixed in 0.23.0
Vendor patch github.com →
Interim mitigation

Upgrade to marimo version 0.23.0 or later which includes the authentication validation fix. If immediate upgrade is not possible, consider network-level restrictions on the /terminal/ws endpoint.

Recommended fix High confidence

0.23.0

  1. Upgrade marimo to version 0.23.0 or later using your Python package manager (e.g., pip install --upgrade marimo>=0.23.0)

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Marimo Exploited in the wild — priority engagement
  • Consultation4.0 h
  • Implementation2.0 h
  • Testing8.0 h
  • Review / QA4.0 h
18.0 hours of engineering $3,080
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-39987 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
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