CVE-2025-2099 Regular Expression Denial of Service (ReDoS) in huggingface/transformers
Attackers can cause denial of service via ReDoS in the transformers library by submitting crafted inputs that trigger exponential backtracking.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-2099?
CVE-2025-2099 is a medium-severity denial of service vulnerability in huggingface/transformers, published on 19 May 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
A vulnerability in the `preprocess_string()` function of the `transformers.testing_utils` module in huggingface/transformers version v4.48.3 allows for a Regular Expression Denial of Service (ReDoS) attack. The regular expression used to process code blocks in docstrings contains nested quantifiers, leading to exponential backtracking when processing input with a large number of newline characters. An attacker can exploit this by providing a specially crafted payload, causing high CPU usage and potential application downtime, effectively resulting in a Denial of Service (DoS) scenario.
Weakness: CWE-1333
Which versions are affected by CVE-2025-2099?
3 open source packages ship an affected version, including transformers. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
transformers PyPI | All versions | 4.49.0 |
transformers PyPI | All versions | 4.50.0 |
transformers PyPI | All versions | 4.50.0 |
Products include Huggingface Transformers.
How do I fix CVE-2025-2099?
Upgrade transformers to a fixed version for your release line: 4.49.0 or 4.50.0.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2025-2099 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-2099 exists.
Other vulnerabilities in huggingface/transformers
- CVE-2023-7018 Deserialization of Untrusted Data in huggingface/transformers
- CVE-2023-6730 Deserialization of Untrusted Data in huggingface/transformers
- CVE-2024-11393 Hugging Face Transformers MaskFormer Model Deserialization of Untrusted Data Remote Code Execution Vulnerability
- CVE-2024-11394 Hugging Face Transformers Trax Model Deserialization of Untrusted Data Remote Code Execution Vulnerability
- CVE-2026-5241 Policy Bypass in LightGlue Nested Config Resolution in huggingface/transformers
Sources
Also known as GHSA-qq3j-4f4f-9583, PYSEC-2025-40.