CVE-2026-55574
HIGHDescription
vLLM is a high-throughput and memory-efficient inference and serving engine for LLMs. Prior to 0.24.0, the structured_outputs.regex API parameter passes a user-supplied regular expression string directly to the grammar compiler backends with no compilation timeout; in the xgrammar backend the string reaches the regex compiler with no guard, and in the outlines backend the validation step blocks structural issues such as lookarounds and backreferences but performs no complexity analysis, so a pattern with nested quantifiers passes all checks and causes exponential state-space expansion, allowing a single request containing an adversarial regex to hang an inference worker indefinitely and deny service. This issue is fixed in version 0.24.0.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Exploit Intelligence
Low risk: more likely to be exploited than 25% of all known CVEs.
References
Related Vulnerabilities
Other CWE-1333 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2023-3364 | High | 7.5 | 44% | - | Fix |
| CVE-2024-8124 | High | 7.5 | 40% | - | Fix |
| CVE-2024-25126 | Medium | 5.3 | 35% | - | Fix |
| CVE-2024-2651 | Medium | 6.5 | 33% | - | Fix |
| CVE-2021-32837 | High | 7.5 | 29% | - | Fix |
| CVE-2024-2829 | High | 7.5 | 26% | - | Fix |
Common questions
How do I fix CVE-2026-55574?
Upgrade vllm to 0.24.0 or later.
Is CVE-2026-55574 being actively exploited?
Not that we know of. CVE-2026-55574 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.32% is the estimated probability that it will be exploited in the next 30 days. That is higher than 25% of all scored CVEs.
How severe is CVE-2026-55574?
CVE-2026-55574 has a CVSS v3 base score of 7.5, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-55574 affect?
Published advisories record a fix for vllm (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-07-07.