Vulnerability in vLLM Inference Engine by vLLM Project
CVE-2026-55574

8.7HIGH

Key Information:

Vendor

Vllm-project

Status
Vllm
Vendor
CVE Published:
6 July 2026

What is CVE-2026-55574?

A vulnerability in the vLLM inference engine allows an attacker to exploit the structured_outputs.regex API parameter, which can lead to denial of service. The issue arises when user-supplied regular expressions are passed to the underlying grammar compiler without proper timeout enforcement. In the xgrammar backend, regular expressions reach the compiler without safeguards, while the outlines backend inadequately checks for structural issues, allowing complex patterns with nested quantifiers. Consequently, an adversarial regex can cause a hanging inference worker, impacting service availability. This vulnerability was addressed in version 0.24.0.

Affected Version(s)

vllm < 0.24.0

References

https://github.com/vllm-project/vllm/security/advisories/...
x_refsource_CONFIRM
https://github.com/vllm-project/vllm/pull/45118
x_refsource_MISC
https://github.com/vllm-project/vllm/commit/2b3006076c5e9...
x_refsource_MISC

CVSS V4

Score:
8.7
Severity:
HIGH
Confidentiality:
None
Integrity:
None
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.