# CVE-2026-39378: nbconvert has an Arbitrary File Read via Path Traversal in HTMLExporter Image Embedding

Source: https://junglewise.ai/threats/cve-2026-39378-nbconvert-has-an-arbitrary-file-read-via-path-traversal-in  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-21. Updated: 2026-05-11  
License: CC BY 4.0 with a link back

CVE-2026-39378 · Severity: medium · CVSS 6.5 · Published 2026-04-21

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.

Technologies: [Jupyter Nbconvert](https://junglewise.ai/threats/technologies/jupyter-nbconvert), [nbconvert (PyPI)](https://junglewise.ai/threats/technologies/nbconvert). Vendors: [Jupyter](https://junglewise.ai/threats/vendors/jupyter), [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2026-39378 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-39378 being exploited in the wild.

**How severe is CVE-2026-39378?** Medium severity, with a CVSS score of 6.5, published 21 April 2026.

**Which products and versions are affected?** nbconvert (PyPI) >= 6.5.0, < 7.17.1, ECOSYSTEM:introduced=6.5.0,fixed=7.17.1.

**Is there a fix for CVE-2026-39378?** Yes. nbconvert (PyPI): upgrade to 7.17.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2026-39378?** Check whether you run Jupyter Nbconvert or nbconvert (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- nbconvert (PyPI): upgrade to 7.17.1 or later

  ```sh
  pip install "nbconvert>=7.17.1"
  ```


## Affected products

- Jupyter Nbconvert
- nbconvert (PyPI) >= 6.5.0, < 7.17.1, ECOSYSTEM:introduced=6.5.0,fixed=7.17.1

## Identifiers

- CVE-2026-39378
- GHSA-7jqv-fw35-gmx9
- PYSEC-2026-2230

## References

- [https://api.github.com/users/g0blinResearch](https://api.github.com/users/g0blinResearch)
- [https://github.com/g0blinResearch](https://github.com/g0blinResearch)
- [https://api.github.com/users/g0blinResearch/gists%7B/gist_id%7D](https://api.github.com/users/g0blinResearch/gists%7B/gist_id%7D)
- [https://api.github.com/users/g0blinResearch/repos](https://api.github.com/users/g0blinResearch/repos)
- [https://avatars.githubusercontent.com/u/11961962?v=4](https://avatars.githubusercontent.com/u/11961962?v=4)
- [https://api.github.com/users/g0blinResearch/events%7B/privacy%7D](https://api.github.com/users/g0blinResearch/events%7B/privacy%7D)

## Related threats

- [Jupyter nbconvert path traversal via output filename metadata](https://junglewise.ai/threats/cve-2026-114140-the-nbconvert-tool-jupyter-nbconvert-converts-jupyter-notebooks)
- [PYSEC-2026-1691 - nbconvert has an uncontrolled search path that leads to unauthorized code execution on Windows](https://junglewise.ai/threats/cve-2025-53000-nbconvert-has-an-uncontrolled-search-path-that-leads-to)
- [Jupyter nbconvert Cross-site Scripting in Mermaid HTML export](https://junglewise.ai/threats/cve-2026-6658-jupyter-nbconvert-cross-site-scripting-in-mermaid-html-export)
- [nbconvert has an Arbitrary File Write via Path Traversal in Cell Attachment Filenames](https://junglewise.ai/threats/cve-2026-39377-nbconvert-has-an-arbitrary-file-write-via-path-traversal-in-cell)
- [nbconvert vulnerable to cross-site scripting (XSS) via multiple exploit paths](https://junglewise.ai/threats/cve-2021-32862-nbconvert-vulnerable-to-cross-site-scripting-xss-via-multiple)