What is CVE-2026-6658?

CVE-2026-6658 is a medium-severity vulnerability in Jupyter Jupyter/jupyter, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2026-06-26.

How severe is CVE-2026-6658?

Medium severity. CVSS v3 base score is 5.4 out of 10.

XSS in Jupyter Jupyter/jupyter

CVE-2026-6658

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.merma…

Vulnerability class: XSS (Cross-Site Scripting)

EPSS: 0.002 (13.3th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N.

Affected products

Jupyter Jupyter/jupyter — versions unspecified

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

security@huntr.dev

Frequently asked questions

What is CVE-2026-6658?: CVE-2026-6658 is a medium-severity vulnerability in Jupyter Jupyter/jupyter, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2026-06-26.
How severe is CVE-2026-6658?: Medium severity. CVSS v3 base score is 5.4 out of 10.