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.

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

Q: 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.

Q: 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.

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, nbconvert (PyPI). Vendors: Jupyter, 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
```
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

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