CVE-2025-6921

High

Description

The huggingface/transformers library, versions prior to 4.53.0, is vulnerable to Regular Expression Denial of Service (ReDoS) in the AdamWeightDecay optimizer. The vulnerability arises from the _do_use_weight_decay method, which processes user-controlled regular expressions in the include_in_weight_decay and exclude_from_weight_decay lists. Malicious regular expressions can cause catastrophic backtracking during the re.search call, leading to 100% CPU utilization and a denial of service. This issue can be exploited by attackers who can control the patterns in these lists, potentially causing the machine learning task to hang and rendering services unresponsive.

SeverityHigh
CVSS7.5
Exploit probability—
ProductHuggingface Transformers
PublishedSep 23, 2025
First seenSep 23, 2025

How to fix

Update
  • huggingface transformers4.53.0 or later
  • transformers4.53.0 or later

Affected products

ProductAffected versionsFixed in
huggingface transformersv < 4.53.04.53.0
transformersPyPIv < 4.53.04.53.0

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CVE-2025-6921 · Huggingface Transformers · Dark Radar