Summary

On Windows, converting a notebook containing SVG output to a PDF results in unauthorized code execution. Specifically, a third party can create a inkscape.bat file that defines a Windows batch script, capable of arbitrary code execution.

When a user runs jupyter nbconvert --to pdf on a notebook containing SVG output to a PDF on a Windows platform from this directory, the inkscape.bat file is run unexpectedly.

Details Give all details on the vulnerability. Pointing to the incriminated source code is very helpful for the maintainer.

nbconvert searches for an inkscape executable when converting notebooks to PDFs here: https://github.com/jupyter/nbconvert/blob/4f61702f5c7524d8a3c4ac0d5fc33a6ac2fa36a7/nbconvert/preprocessors/svg2pdf.py#L104

The MITRE page on CWE-427 (Uncontrolled Search Path Element) summarizes the root cause succinctly:

In Windows-based systems, when the LoadLibrary or LoadLibraryEx function is called with a DLL name that does not contain a fully qualified path, the function follows a search order that includes two path elements that might be uncontrolled: - the directory from which the program has been loaded - the current working directory

PoC

Complete instructions, including specific configuration details, to reproduce the vulnerability.

1. Create a directory containing:

- A hidden bat file called inkscape.bat containing msg "You've been hacked!"

- A dummy ipynb file called MachineLearning.ipynb

2. Run the command jupyter nbconvert --to pdf MachineLearning.ipynb.

3. Wait a few seconds, and you should see a popup showing the message "You've been hacked!"

Impact

All Windows users.

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).