CVE-2025-6921: Hugging Face Transformers vulnerable to Regular Expression Denial of Service (ReDoS) in the AdamWeightDecay optimizer

CVE-2025-6921 · Severity: low · CVSS 3 · Published 2026-07-07

Hugging Face Transformers vulnerable to Regular Expression Denial of Service (ReDoS) in the AdamWeightDecay optimizer

Technologies: transformers (PyPI). Vendors: PyPI.

Quick answers

Is CVE-2025-6921 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2025-6921 being exploited in the wild.
How severe is CVE-2025-6921?
Low severity, with a CVSS score of 3, published 7 July 2026.
Which products and versions are affected?
transformers (PyPI) ECOSYSTEM:introduced=0,fixed=4.53.0.
Is there a fix for CVE-2025-6921?
Yes. transformers (PyPI): upgrade to 4.53.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
Am I affected by CVE-2025-6921?
Check whether you run transformers (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • transformers (PyPI): upgrade to 4.53.0 or later
    pip install "transformers>=4.53.0"

Affected products

  • transformers (PyPI) ECOSYSTEM:introduced=0,fixed=4.53.0

Identifiers

  • CVE-2025-6921
  • GHSA-4w7r-h757-3r74
  • PYSEC-2026-1980

This page as Markdown. Free to reuse under CC BY 4.0 with a link back.