CVE-2026-39987Known exploitationPublic exploitNetwork attack vector

Unauthenticated code execution via unvalidated terminal WebSocket

Published Apr 9, 2026 · Updated Apr 9, 2026

Missing authentication in Marimo Inc. marimo before 0.23.0 allows remote attackers to execute system commands through /terminal/ws. The endpoint accepts a WebSocket and calls pty.fork() without validate_auth(), exposing the spawned interactive shell to untrusted clients. The server must run in edit mode on a non-Windows host with terminal support; a single unauthenticated connection gains the marimo process account's privileges.

CVSS severity9.8
Critical
EPSS probability98.95%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Missing authentication in Marimo Inc. marimo before 0.23.0 allows remote attackers to execute system commands through /terminal/ws. The endpoint accepts a WebSocket and calls pty.fork() without validate_auth(), exposing the spawned interactive shell to untrusted clients. The server must run in edit mode on a non-Windows host with terminal support; a single unauthenticated connection gains the marimo process account's privileges.

The record

CVE
CVE-2026-39987
Published
Apr 9, 2026
Updated
Apr 9, 2026
Vendor
Marimo Inc.
Product
marimo
Classifications
CWE-306, T1059.004, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 9, 2026Record updatedLatest update available in the CVE record.
  3. Apr 12, 2026Exploitation reportedNKAbuse botnet deployment through exploited marimo servers

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 0.23.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Marimo Inc. · marimoversion=< 0.23.0

Published CVSS scores

9.3GitHub, Inc.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
9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationReported
Public exploitPublished

Weakness, pattern, technique

CWE-306Missing Authentication for Critical Function
T1059.004Unix Shell
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Reported exploitation

Technologies

Your stack

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Your stack

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