{"id":"CVE-2026-6658","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-6658","summary":"jupyter/nbconvert allows Cross-site Scripting (XSS) via unsanitized `text/vnd.mermaid` output in HTML exports","details":"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.","published":"2026-06-26T12:30:29Z","modified":"2026-11-06T18:00:04.178054901Z","cvss":{"score":5.4,"severity":"MEDIUM","vector":"CVSS:3.0/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"nbconvert","fixedVersion":null}],"fix":null,"references":[{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-6658"},{"type":"PACKAGE","url":"https://github.com/jupyter/nbconvert"},{"type":"WEB","url":"https://huntr.com/bounties/47570290-3b26-4477-8cfa-fdef7db5aefe"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-11-06T18:00:04.178054901Z"}}