Known exploited vulnerability
CVE-2026-39987
The short answer
CVE-2026-39987 affects marimo-team marimo and is rated critical (CVSS 9.3). CISA added it to the Known Exploited Vulnerabilities catalog on 2026-04-23: attackers are using it, so patch it first. Fixed versions are published for marimo (0.23.0).
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 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.
Weakness: CWE-306.
Severity
9.3 critical
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Exploited (CISA KEV)
Yes, since Apr 23, 2026
Federal due date May 7, 2026
EPSS, next 30 days
100%
Higher than 100% of scored CVEs
How it can be exploited
- Attack vector
- Network
- Attack complexity
- Low
- Attack requirements
- None
- Privileges required
- None
- User interaction
- None
- Confidentiality impact
- High
- Integrity impact
- High
- Availability impact
- High
What CISA says to do
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Affected packages and fixed versions
| Package | Ecosystem | Fixed in | Advisory |
|---|---|---|---|
| marimo | PyPI | 0.23.0 | GHSA-2679-6mx9-h9xc |
Is it in your code? Drop your lockfile into the free vulnerability check, or let vulnerability watch check your repository every day and open the upgrade as a pull request.
Affected products
marimo. NVD's record lists the exact affected versions.
References
- github.com/marimo-team/marimo/commit/c24d4806398f30be6b12acd6c60d1d7c68cfd12a Patch
- github.com/marimo-team/marimo/pull/9098 Issue TrackingPatch
- github.com/marimo-team/marimo/security/advisories/GHSA-2679-6mx9-h9xc ExploitMitigationVendor Advisory
- www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-39987 US Government Resource
- www.sysdig.com/blog/marimo-oss-python-notebook-rce-from-disclosure-to-exploitation-in-under-10-hours ExploitThird Party Advisory
Questions
Is CVE-2026-39987 being exploited?
Yes. CISA added CVE-2026-39987 to its Known Exploited Vulnerabilities catalog on 2026-04-23, with a federal remediation due date of 2026-05-07.
How do I fix CVE-2026-39987?
Upgrade to a fixed version: marimo (PyPI) 0.23.0. CISA's 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.
From NVD, CISA KEV, FIRST EPSS and OSV.dev, checked . Status on NVD: Analyzed. The description is NVD's text, quoted as published.
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