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CVE-2025-6921

Huggingface Transformers denial of service

7.5 HIGHPublic exploitEPSS 0.51%
  1. Published23 Sept 2025

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 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityNone
IntegrityNone
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

Huggingface Transformers< 4.53.0

Remediation

Fixed in
Huggingface Transformers≥ 4.53.0

References

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Frequently asked

Is CVE-2025-6921 being actively exploited?

CVE-2025-6921 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.51%.

How severe is CVE-2025-6921?

CVE-2025-6921 has a CVSS 3.1 base score of 7.5, rated high. EPSS estimates a 0.51% probability of exploitation.

Which products are affected by CVE-2025-6921?

Affected products include Huggingface Transformers.

How do I fix CVE-2025-6921?

Upgrade affected software to a fixed version, for example Huggingface Transformers 4.53.0 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2025-6921 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.