MEDIUM5.3

PYSEC-2026-1981

Hugging Face Transformers is vulnerable to ReDoS through its MarianTokenizer

Quick fix

PYSEC-2026-1981 — transformers: upgrade to the fixed version with the command below.

pip install --upgrade 'transformers>=4.53.0'

Details

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.

Are you affected?

Enter the version of the package you're using.

Affected packages

PyPI/transformers

Introduced in: 0Fixed in: 4.53.0

Fixpip install --upgrade 'transformers>=4.53.0'

References

https://nvd.nist.gov/vuln/detail/CVE-2025-6638[ADVISORY]
https://github.com/huggingface/transformers/commit/47c34fba5c303576560cb29767efb452ff12b8be[WEB]
https://github.com/huggingface/transformers/commit/d37f7517972f67e3f2194c000ed0f87f064e5099[WEB]
https://github.com/huggingface/transformers[PACKAGE]
https://huntr.com/bounties/6a6c933f-9ce8-4ded-8b3b-2c1444c61f36[WEB]
https://pypi.org/project/transformers[PACKAGE]
https://github.com/advisories/GHSA-59p9-h35m-wg4g[ADVISORY]