In short
- CVE-2026-39377 is a MEDIUM (CVSS 6.5) vulnerability affecting nbconvert, nbconvert (jupyter).
- Chance of exploitation in the next 30 days (EPSS): 0.27%, higher than 18.6% of all vulnerabilities.
- Fix: update to 7.17.1 or later.
| Package | Affected versions | Patched versions |
|---|
| nbconvert PyPI | ≥ 6.5.0, < 7.17.1
| 7.17.1
|
| nbconvert | ≥ 6.5.0, < 7.17.1
| 7.17.1
|
Description
Arbitrary File Write via Path Traversal in Cell Attachment Filenames
Summary
nbconvert allows 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.
Impact
This vulnerability allows writing files with arbitrary content to arbitrary filesystem locations, limited only by the permissions of the process running nbconvert. The attacker controls:
- Full destination path (via
../ traversal)
- Filename
- File extension
- File content
Patches
- upgrade to nbconvert v7.17.1
Workarounds
disable ExtractAttachmentsPreprocessor by setting:
c. ExtractAttachmentsPreprocessor.enabled = False
NVD 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.
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