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

> Attackers can cause service disruption and resource exhaustion in Hugging Face Transformers by submitting crafted numeric strings to the number normalization method.

- **Severity:** Medium 5.3 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 14 Sep 2025
- **Updated:** 15 Sep 2025
- **Also known as:** GHSA-rcv9-qm8p-9p6j, PYSEC-2026-1988

## What is CVE-2025-6051?

CVE-2025-6051 is a medium-severity denial of service vulnerability in huggingface/transformers, published on 14 Sep 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-1333 (Inefficient Regular Expression Complexity)

## Which versions are affected by CVE-2025-6051?

3 open source packages ship an affected version, including transformers. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `transformers` | PyPI | All versions | 4.53.0 |
| `transformers` | PyPI | All versions | 4.53.0 |
| `transformers` | PyPI | All versions | 4.53.0 |

Products: Huggingface Transformers.

## How do I fix CVE-2025-6051?

Upgrade transformers to 4.53.0 or later.

## Is CVE-2025-6051 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-6051 exists.

## Other vulnerabilities in huggingface/transformers

- [CVE-2023-7018](https://insights.sbomify.com/CVE-2023-7018/): Deserialization of Untrusted Data in huggingface/transformers (critical 9.6)
- [CVE-2023-6730](https://insights.sbomify.com/CVE-2023-6730/): Deserialization of Untrusted Data in huggingface/transformers (critical 9.0)
- [CVE-2024-11393](https://insights.sbomify.com/CVE-2024-11393/): Hugging Face Transformers MaskFormer Model Deserialization of Untrusted Data Remote Code Execution Vulnerability (high 8.8)
- [CVE-2024-11394](https://insights.sbomify.com/CVE-2024-11394/): Hugging Face Transformers Trax Model Deserialization of Untrusted Data Remote Code Execution Vulnerability (high 8.8)
- [CVE-2026-5241](https://insights.sbomify.com/CVE-2026-5241/): Policy Bypass in LightGlue Nested Config Resolution in huggingface/transformers (high 8.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-6051 and fix it if it is affected.

What it is: CVE-2025-6051 is a medium-severity denial of service vulnerability in huggingface/transformers, published on 14 Sep 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-6051 exists.

Affected packages and fixed versions:
- transformers (PyPI): affected all versions; fixed in 4.53.0
- transformers (PyPI): affected all versions; fixed in 4.53.0
- transformers (PyPI): affected all versions; fixed in 4.53.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-6051/ (Markdown: https://insights.sbomify.com/CVE-2025-6051/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-6051
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-6051
- OSV: https://osv.dev/vulnerability/CVE-2025-6051

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-6051/
Summaries are generated and may contain mistakes; the official description above is the record.