CVE-2026-57516 is a high-severity vulnerability affecting Anyscale, Inc's Ray product prior to version 2.56.0. The issue is an unsafe deserialization vulnerability in the WebDataset reader component. Specifically, the _default_decoder() function in webdataset_datasource.py calls pickle.loads() on tar archive entries with .pkl or .pickle extensions and torch.load() with weights_only=False on .pt or .pth files without validation. This allows an attacker who can supply a crafted tar archive to the read_webdataset() function to execute arbitrary code on every Ray remote worker that processes the malicious archive. The vulnerability has a CVSS 4.0 score of 8.6, indicating high severity. No official patch or remediation level is currently stated in the available data.

Successful exploitation results in remote code execution within Ray remote workers that process the malicious tar archive. This can lead to full compromise of the affected worker processes, potentially allowing attackers to execute arbitrary commands or code within the environment running Ray. The vulnerability affects all deployments using the vulnerable versions of Ray that utilize the WebDataset reader functionality.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is released, avoid processing untrusted or unauthenticated tar archives with the read_webdataset() function. Restrict access to the functionality that accepts WebDataset inputs to trusted sources only. Monitor vendor communications for updates regarding patches or official mitigations.