huggingface transformers up to 4.52.x MarianTokenizer remove_language_code redos

Summaryinfo

A vulnerability labeled as problematic has been found in huggingface transformers up to 4.52.x. This affects the function remove_language_code of the component MarianTokenizer. The manipulation results in redos. This vulnerability is known as CVE-2025-6638. It is possible to launch the attack remotely. No exploit is available. The affected component should be upgraded.

Detailsinfo

A vulnerability, which was classified as problematic, was found in huggingface transformers up to 4.52.x. Affected is the function remove_language_code of the component MarianTokenizer. 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. CVE summarizes:

A Regular Expression Denial of Service (ReDoS) vulnerability was discovered in the Hugging Face Transformers library, specifically affecting the MarianTokenizer's `remove_language_code()` method. This vulnerability is present in version 4.52.4 and has been fixed in version 4.53.0. The issue arises from inefficient regex processing, which can be exploited by crafted input strings containing malformed language code patterns, leading to excessive CPU consumption and potential denial of service.

The advisory is shared for download at huntr.com. This vulnerability is traded as CVE-2025-6638 since 06/25/2025. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1449.003.

Upgrading to version 4.53.0 eliminates this vulnerability. Applying the patch 47c34fba5c303576560cb29767efb452ff12b8be 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.

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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/

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