Vulnerability · Published Sep 23, 2025 · Assigned by @huntr_ai
CVE-2025-6921Regular Expression Denial of Service (ReDoS) in huggingface/transformers
Medium 5.3
In plain English
A medium-severity uncontrolled resource consumption in huggingface/transformers from huggingface. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 44% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| PyPI | transformers | 4.53.0 | GHSA-4w7r-h757-3r74 |
| PyPI | transformers | 4.53.0 | PYSEC-2026-1980 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| huggingface | huggingface/transformers | unspecified – before 4.53.0 |
Weakness: CWE-400 · Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L