CVE-2026-39377

Description

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.

CVSS v3.1 Score

6.5

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

EPSS — Exploit Prediction

0.0004

Probability of exploitation

0.13%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-22 Path Traversal

CWE-73 CWE-73

Affected Products

Vendor	Product	Versions
jupyter	nbconvert	6.5.0 — 7.17.1

References

Advisories & Patches

https://github.com/jupyter/nbconvert/security/advisories/GHSA-4c99-qj7h-p3vg

Other References

https://github.com/jupyter/nbconvert/releases/tag/v7.17.1

Frequently Asked Questions

What is CVE-2026-39377? +

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. It has a CVSS v3.1 base score of 6.5 (MEDIUM).

How severe is CVE-2026-39377? +

CVE-2026-39377 has a CVSS v3.1 score of 6.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0004, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-39377? +

CVE-2026-39377 affects products from jupyter, specifically: nbconvert. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-39377? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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