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:

python c. ExtractAttachmentsPreprocessor.enabled = False

Summary

When HTMLExporter.embedimages=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.

Patches

Upgrade to nbconvert 7.17.1

Workarounds

Do not enable HTMLExporter.embedimages (it is not enabled by default).