29 May 2026
Reference: CVE-2026-39987
1. What is being reported?
The Marimo software had a security gap where one of its web communication points did not check if users were authorised. This allowed anyone to connect and execute commands on the computer running Marimo, without needing a password or login.
2. What this means in plain English
If your organisation uses Marimo for coding or data tasks, an attacker could exploit this flaw to access your system, steal data, or cause damage. This is a high-risk problem because it does not require the attacker to be logged in or have any credentials.
3. Could this affect a small business?
Small businesses or charities using Marimo notebooks, especially older versions before 0.23.0, could be at risk. If you do not use Marimo or similar Python notebook tools, this vulnerability probably does not affect you.
4. What to do now
- Check if your organisation uses Marimo software for any tasks.
- If you do, verify the version and update immediately to version 0.23.0 or later.
- Ask your IT provider to review your systems for any signs of unauthorised access related to this vulnerability.
- Ensure your network and software are regularly updated and monitored for unusual activity.
5. Ask your IT provider
Can you confirm if we use Marimo Python notebook software, and if so, have we updated it to version 0.23.0 or later to fix the critical security vulnerability CVE-2026-39987?
6. Bottom line
Update Marimo software promptly if you use it to prevent unauthorised access and protect your systems.
Information based on NVD, CISA KEV, and reputable security news reporting.