CVE-2026-39377: Jupyter Nbconvert

Medium severity, CVSS 6.5. EPSS: 0.4% chance of exploitation in the next 30 days.

The nbconvert tool, jupyter nbconvert, converts Jupyter notebooks to various other formats via Jinja templates. Versions 6.5 through 7.17.0 allow arbitrary file writes to locations outside the intended output directory when processing notebooks containing crafted cell attachment filenames. The `ExtractAttachmentsPreprocessor` passes attachment filenames directly to the filesystem without sanitization, enabling path traversal attacks. This vulnerability provides complete control over both the destination path and file extension. Version 7.17.1 contains a patch.

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.