CVE-2026-39378: Jupyter Nbconvert

Medium severity, CVSS 6.5. EPSS: 0.5% chance of exploitation in the next 30 days.

The nbconvert tool, jupyter nbconvert, converts Jupyter notebooks to various other formats via Jinja templates. In versions 6.5 through 7.17.0, when `HTMLExporter.embed_images=True`, nbconvert's markdown renderer allows arbitrary file read via path traversal in image references. A malicious notebook can exfiltrate sensitive files from the conversion host by embedding them as base64 data URIs in the output HTML. nbconvert 7.17.1 contains a fix. As a workaround, do not enable `HTMLExporter.embed_images`; it is not enabled by default.

Affected products

• Jupyter Nbconvert: from 6.5.0, before 7.17.1 (fixed in 7.17.1)

Published 2026-04-21. Last modified 2026-06-17.