Gradio is Vulnerable to Absolute Path Traversal on Windows with Python 3.13+

Summary

Gradio apps running on Window with Python 3.13+ are vulnerable to an absolute path traversal issue that enables unauthenticated attackers to read arbitrary files from the file system.

Details

Python 3.13+ changed the definition of os.path.isabs so that root-relative paths like /windows/win.ini on Windows are no longer considered absolute paths, resulting in a vulnerability in Gradio's logic for joining paths safely.

This can be exploited by unauthenticated attackers to read arbitrary files from the Gradio server, even when Gradio is set up with authentication.

PoC

% curl http://10.10.10.10:7860/static//windows/win.ini
; for 16-bit app support
[fonts]
[extensions]
[mci extensions]
[files]
[Mail]
MAPI=1

Impact

Arbitrary file read in the context of the Windows user running Gradio.