Ray versions 2.54.0 to before 2.55.0 register custom Arrow extension types globally in PyArrow. When PyArrow reads a Parquet file with these extension types, it calls __arrow_ext_deserialize__ on the metadata bytes. Ray's implementation passes these bytes directly to cloudpickle.loads(), enabling arbitrary code execution during schema parsing. This vulnerability is identified as CWE-94 (Improper Control of Generation of Code) and CWE-502 (Deserialization of Untrusted Data). The issue is fixed in Ray version 2.55.0.

An attacker can achieve arbitrary code execution on a system processing malicious Parquet files with crafted metadata, exploiting the deserialization process before any data rows are read. This can lead to full system compromise or unauthorized actions within the context of the Ray process. The CVSS 4.0 score is 8.9, indicating high severity with network attack vector, low attack complexity, and partial user interaction required.

This vulnerability is patched in Ray version 2.55.0. Users should upgrade to version 2.55.0 or later to remediate this issue. No official remediation level or temporary fix is indicated beyond upgrading. Patch status is confirmed by the vendor advisory stating the fix is included in 2.55.0. Until upgrading, avoid processing untrusted Parquet files containing the affected Arrow extension types.