NBCONVERT · CVE-2026-6658 · Package
NO FIX YET
nbconvert renders text/vnd.mermaid cell output into HTML exports without escaping, so a crafted notebook can break out of a pre tag. A person who opens the exported HTML then runs attacker-chosen JavaScript in that page.
first public Jun 26, 2026 · 1 source
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Any system that uses nbconvert to turn notebooks into HTML, especially if the notebooks come from users or outside sources. The exposure is in the exported HTML viewed by a person, so a pipeline that only executes notebooks and never publishes or views the HTML is less exposed. The sources do not state a fixed version.
Not affected if html-export-unused, no-untrusted-notebooks
Who cares cwe-79, jupyter, jupyterlab, nbconvert, python
pip show nbconvert and compare the version with 7.17.0 or lower.No fix yet, per the sources.
A vulnerability in jupyter/nbconvert versions <= 7.17.0 allows for Cross-site Scripting (XSS) via unsanitized text/vnd.mermaid output in HTML exports. The data_mermaid block in share/templates/lab/base.html.j2 renders text/vnd.mermaid cell output directly into HTML without escaping, enabling attackers to inject arbitrary HTML/JavaScript by breaking out of the <pre> tag. This vulnerability impacts any server using nbconvert to render notebooks as HTML, allowing attackers to execute arbitrary JavaScript in the context of users viewing the HTML export.
This page as .md · .json · CVSS:3.0/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
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