CVE-2026-66007 is a path traversal vulnerability affecting huggingface datasets through version 5.0.0. The vulnerability arises because the file_name metadata field in folder-based dataset builders is not properly validated before being concatenated with the dataset directory path. Attackers can exploit this by supplying crafted file_name values containing directory traversal sequences (e.g., '../') to read arbitrary local files. These files can then be embedded into the output when the dataset is saved to disk or pushed to the hub. The vulnerability was fixed in a commit identified as f989ef9, but no official patch version is specified in the provided data.

An attacker can read arbitrary local files on the system where the huggingface datasets library is used by exploiting the improper validation of the file_name metadata field. This can lead to unauthorized disclosure of sensitive local files embedded into dataset outputs. The vulnerability requires no privileges and no user interaction but has a medium severity impact according to the CVSS 4.0 score of 6.9.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. The vulnerability was fixed in a commit (f989ef9), so upgrading to a version including this fix is recommended once available. Until then, avoid processing untrusted datasets with folder-based dataset builders or applying save_to_disk or push_to_hub operations on untrusted inputs.