CVE-2025-48943: vllm Denial of Service Vulnerability Due to Invalid Regex Input
Summary
CVE-2025-48943: vLLM is an inference and serving engine for large language models (LLMs). Affects vllm across 2 version ranges.
>= 0.8.0, < 0.9.0
< 08bf7840780980c7568c573c70a6a8db94fd45ff
Fixed in 08bf7840780980c7568c573c70a6a8db94fd45ff. How to fix ↓
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Background
vLLM is an inference and serving engine designed for large language models (LLMs). It enables efficient deployment and management of LLMs, providing features such as structured output handling. However, certain versions of vLLM are susceptible to a Denial of Service (DoS) attack when invalid regular expressions are used, leading to server crashes.
Vulnerability Detail
The vulnerability identified as CVE-2025-48943 affects vLLM versions from 0.8.0 up to, but not including, 0.9.0. It arises from improper handling of invalid regex patterns during structured output processing. When an invalid regex is provided, the vLLM server can crash, resulting in a Denial of Service. This issue is similar to a previously identified vulnerability (GHSA-6qc9-v4r8-22xg/CVE-2025-48942) but specifically pertains to regex rather than JSON schema validation.
How To Fix
Latest published version: 0.32.0 as of 22 Oct 2026
pip install --upgrade "vllm==0.32.0"Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
08bf7840780980c7568c573c70a6a8db94fd45ff
This is the first release that contains the fix.
pip install --upgrade "vllm==08bf7840780980c7568c573c70a6a8db94fd45ff"Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary measure, avoid using invalid regex patterns in your structured output configurations. Ensure that all regex inputs are validated before being processed by the vLLM server.
Conclusion
CVE-2025-48943 presents a significant risk to users of vLLM versions 0.8.0 to 0.9.0 due to its potential to cause Denial of Service through invalid regex inputs. Users are strongly advised to upgrade to version 0.9.0 or later to mitigate this risk.
See every vulnerability recorded for vllm →
FAQ
The impact of this vulnerability is a Denial of Service, where the vLLM server can crash if an invalid regex is provided, disrupting service availability.
Versions of vLLM from 0.8.0 up to, but not including, 0.9.0 are affected by this vulnerability.
You can use the Vulert playground at Vulert Scanner to check if your application is affected by this vulnerability without requiring any signup.
If you cannot update immediately, ensure that you validate all regex inputs to prevent the server from crashing.
More information can be found in the advisory database at https://github.com/pypa/advisory-database/blob/main/vulns/vllm/PYSEC-2025-55.yaml.
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