CVE-2026-39987

marimo Affected by Pre-Auth Remote Code Execution via Terminal WebSocket Authentication Bypass

CVSS 4.0 Critical 9.3Known exploited (CISA KEV)

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

Description

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.

Key data

CVSS 4.0 Critical 9.3

Score published by GitHub_M in the CVE record.

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

Attack vector: Network
The vulnerable component can be reached over a network, possibly from the Internet.
Attack complexity: Low
No measurable action is needed to get around the system's built-in security controls. The attack is repeatable.
Attack requirements: None
The attack works without any special deployment or execution conditions.
Privileges required: None
No account or privileges are needed.
User interaction: None
No action from any user is needed.
Vulnerable system: confidentiality: High
Serious or total effect on the secrecy of data.
Vulnerable system: integrity: High
Serious or total effect on the trustworthiness of data.
Vulnerable system: availability: High
Serious or total effect on availability.
Subsequent systems: confidentiality: None
No effect on other systems' data secrecy.
Subsequent systems: integrity: None
No effect on other systems' data trustworthiness.
Subsequent systems: availability: None
No effect on other systems' availability.

Metric	Value	What it means
Attack vector	Network	The vulnerable component can be reached over a network, possibly from the Internet.
Attack complexity	Low	No measurable action is needed to get around the system's built-in security controls. The attack is repeatable.
Attack requirements	None	The attack works without any special deployment or execution conditions.
Privileges required	None	No account or privileges are needed.
User interaction	None	No action from any user is needed.
Vulnerable system: confidentiality	High	Serious or total effect on the secrecy of data.
Vulnerable system: integrity	High	Serious or total effect on the trustworthiness of data.
Vulnerable system: availability	High	Serious or total effect on availability.
Subsequent systems: confidentiality	None	No effect on other systems' data secrecy.
Subsequent systems: integrity	None	No effect on other systems' data trustworthiness.
Subsequent systems: availability	None	No effect on other systems' availability.

CVSS is owned and managed by FIRST.Org, Inc. (FIRST) and is used by permission. Each CVSS score on this site is shown together with its vector string, as published in the CVE record by the source named next to it. Learn more at first.org/cvss.

EPSS

Exploit Prediction Scoring System by FIRST: an estimate of the probability that exploitation activity will be observed in the next 30 days.

Score: 0.99743 (99.7% probability)
Percentile: 99.95%
Scores of: Nov 10, 2026
Model: v2026.06.15

CISA Known Exploited Vulnerabilities

This CVE is listed in the CISA KEV catalog.

Name in the catalog: Marimo Remote Code Execution Vulnerability
Added to the catalog: Apr 23, 2026
Federal due date: May 7, 2026

CISA assessment as of Apr 23, 2026

Stakeholder-Specific Vulnerability Categorization (SSVC) decision points added by CISA.

Exploitation: Recorded by CISA as active
Automatable: yes
Technical impact: total

Weakness (CWE)

CWE catalog version 5.0.

CWE-306Missing Authentication for Critical Functionality

Affected products

Products listed in the CVE record, as the CNA published them.

marimo-team marimo
- affected: < 0.23.0

References

Links listed in the CVE record. They lead to other sites, which CubePath does not control.

Timeline

ID reservedApr 8, 2026
Record publishedApr 9, 2026
Added to CISA KEVApr 23, 2026
Record last updatedApr 24, 2026

Look up another CVE

About CubePath

CubePath is a cloud provider with data centers in Europe and the United States. It offers VPS, bare metal servers and DDoS protection.

Cloud VPS DDoS protection

Data from the CVE Program (MITRE), CISA KEV and FIRST EPSS. CVSS is owned by FIRST and used by permission. Not affiliated with or endorsed by MITRE, CISA or FIRST. Data as of Nov 10, 2026, 19:52 UTC. Sources and licenses