huggingface transformers up to 4.52.x normalize_numbers redos

Summaryinfo

A vulnerability was found in huggingface transformers up to 4.52.x. It has been rated as problematic. Affected is the function normalize_numbers. Performing a manipulation results in redos. This vulnerability was named CVE-2025-6051. The attack may be initiated remotely. There is no available exploit. Upgrading the affected component is advised.

Detailsinfo

A vulnerability classified as problematic has been found in huggingface transformers up to 4.52.x. This affects the function normalize_numbers. The manipulation with an unknown input leads to a redos vulnerability. CWE is classifying the issue as CWE-1333. The product uses a regular expression with an inefficient, possibly exponential worst-case computational complexity that consumes excessive CPU cycles. This is going to have an impact on availability. The summary by CVE is:

A Regular Expression Denial of Service (ReDoS) vulnerability was discovered in the Hugging Face Transformers library, specifically within the `normalize_numbers()` method of the `EnglishNormalizer` class. This vulnerability affects versions up to 4.52.4 and is fixed in version 4.53.0. The issue arises from the method's handling of numeric strings, which can be exploited using crafted input strings containing long sequences of digits, leading to excessive CPU consumption. This vulnerability impacts text-to-speech and number normalization tasks, potentially causing service disruption, resource exhaustion, and API vulnerabilities.

It is possible to read the advisory at huntr.com. This vulnerability is uniquely identified as CVE-2025-6051 since 06/13/2025. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1449.003 according to MITRE ATT&CK.

Upgrading to version 4.53.0 eliminates this vulnerability. Applying the patch ba8eaba9865618253f997784aa565b96206426f0 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2025-29125). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Vendor

• huggingface

Name

• transformers

Version

• 4.0
• 4.1
• 4.2
• 4.3
• 4.4
• 4.5
• 4.6
• 4.7
• 4.8
• 4.9
• 4.10
• 4.11
• 4.12
• 4.13
• 4.14
• 4.15
• 4.16
• 4.17
• 4.18
• 4.19
• 4.20
• 4.21
• 4.22
• 4.23
• 4.24
• 4.25
• 4.26
• 4.27
• 4.28
• 4.29
• 4.30
• 4.31
• 4.32
• 4.33
• 4.34
• 4.35
• 4.36
• 4.37
• 4.38
• 4.39
• 4.40
• 4.41
• 4.42
• 4.43
• 4.44
• 4.45
• 4.46
• 4.47
• 4.48
• 4.49
• 4.50
• 4.51
• 4.52

License

• open-source

Website

• Product: https://github.com/huggingface/transformers/

CPE 2.3info

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CPE 2.2info

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Entryinfo

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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