Apache C++ Parquet and PyArrow versions 4.0.0 through 25.0.1 allow unvalidated KMS URLs to be passed through to KMS clients. This can lead to a KMS token being sent to a malicious host if the KMS URL is controlled by an attacker via a Parquet file. Version 26.0.0 disables this behavior by default and requires explicit opt-in to allow file-controlled KMS URLs.