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Vulnerability record · CVE-2025-6921 · published 23 September 2025

CVE-2025-6921: Huggingface transformers uncontrolled resource consumption vulnerability

Huggingface · Transformers

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.

7.5 CVSS 3.1 High EPSS 0.51% · top 58.8% CWE-400 · Uncontrolled resource consumption
7.5CVSS 3.1 base score
0.51%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
2References, 1 tagged exploit
17 Jun 2026Last modified by NVD

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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/huggingface/transformers/commit/47c34fba5c303576560cb29767efb452ff12b8be Patch
https://huntr.com/bounties/287d15a7-6e7c-45d2-8c05-11e305776f1f ExploitThird Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2025-6921), CISA KEV, FIRST EPSS (scores of 2026-09-29). This page is refreshed as NVD updates the record.