Inefficient regular expression complexity in vLLM - CVE-2026-55574
Published: July 2, 2026
Vulnerability identifier: #VU136793
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-55574
CWE-ID: CWE-1333
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: vLLM
Affected software:
vLLM
vLLM
Detailed vulnerability description
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to inefficient regular expression complexity in the structured_outputs.regex API in the xgrammar and outlines backends when compiling a user-supplied regex string. A remote attacker can send a specially crafted regex pattern to cause a denial of service.
A single crafted request can hang an inference worker indefinitely.
How to mitigate CVE-2026-55574
Install security update from vendor's website.