PYSEC-2025-55: vLLM allows clients to crash the openai server with invalid regex

Q: Which deployments are affected?

vLLM versions 0.8.0 through versions before 0.9.0 are affected when structured output is used with regex input. Version 0.9.0 fixes the issue.

Q: What access does an attacker need?

An attacker needs network access to the vLLM server and low-privileged access sufficient to submit a structured-output request containing an invalid regex. No user interaction is required.

Q: What is the impact of successful exploitation?

A malformed regex can cause the vLLM OpenAI server to crash, resulting in denial of service. The provided impact data indicates availability impact only, with no confidentiality or integrity impact.

Published May 30, 2025

Updated

vLLM is an inference and serving engine for large language models (LLMs). Version 0.8.0 up to but excluding 0.9.0 have a Denial of Service (ReDoS) that causes the vLLM server to crash if an invalid regex was provided while using structured output. This vulnerability is similar to GHSA-6qc9-v4r8-22xg/CVE-2025-48942, but for regex instead of a JSON schema. Version 0.9.0 fixes the issue.

Affected Software

1 affected component

vllm vllm>=0.8.0<0.9.0

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
Upgrade vLLM to a version that resolves this vulnerability.
Fixed in 0.9.0

Event History

May 30, 2025

CVE Published

via OSV·06:36 PM

Data Sourced

via OSV·06:36 PM

DescriptionSeverityWeakness

Frequently Asked Questions

Which deployments are affected?

vLLM versions 0.8.0 through versions before 0.9.0 are affected when structured output is used with regex input. Version 0.9.0 fixes the issue.

What access does an attacker need?

An attacker needs network access to the vLLM server and low-privileged access sufficient to submit a structured-output request containing an invalid regex. No user interaction is required.

What is the impact of successful exploitation?

A malformed regex can cause the vLLM OpenAI server to crash, resulting in denial of service. The provided impact data indicates availability impact only, with no confidentiality or integrity impact.

PYSEC-2025-55: vLLM allows clients to crash the openai server with invalid regex

Affected Software

Remediation

Event History

Frequently Asked Questions

Which deployments are affected?

What access does an attacker need?

What is the impact of successful exploitation?

Company

Resources

Contact

Frequently Asked Questions

Which deployments are affected?

What access does an attacker need?

What is the impact of successful exploitation?