CVE-2026-55574 vllm vulnerability
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.
Quick answer
vllm should be reviewed and updated if it matches the affected versions. The recommended fix is to apply the vendor-supported patched version or the mitigation steps below, then retest the public website with Fixnx.
Who is affected
Affected versions
- Review vendor advisory for affected versions.
Fixed versions
- Apply the latest vendor-supported patched version.
How to fix it
vLLM is affected by CVE-2026-55574, a security exposure. vLLM is a high-throughput and memory-efficient inference and serving engine for LLMs. The recommended remediation is to update to vLLM 0.24.0 or later. Until the update is complete, restrict structured_outputs.regex inputs and apply request timeouts and worker isolation until patched, review logs, and reduce exposure of the affected service or workflow.
- Inventory every deployment, package, appliance, container, service, and managed environment that uses vLLM.
- Confirm the installed version and compare it with versions prior to 0 and the source advisory for CVE-2026-55574.
- Apply the vendor-supported fix: update to vLLM 0.24.0 or later.
- If the update cannot be applied immediately, restrict structured_outputs.regex inputs and apply request timeouts and worker isolation until patched; disable unnecessary public access, endpoints, integrations, uploads, management interfaces, or high-risk features until patched.
- Review application, device, reverse-proxy, WAF, package manager, container, authentication, and audit logs for activity related to CVE-2026-55574.
- Rotate sessions, API tokens, service credentials, integration keys, and administrator passwords if logs or affected data indicate compromise, code execution, credential exposure, or unauthorized access.
- Clear caches, restart affected services, rebuild affected containers or appliances when appropriate, and remove temporary files, stored payloads, generated artifacts, or unsafe configuration created during exploitation attempts.
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Verify the fix
- Confirm vLLM now reports vLLM 0.24.0 or later or a later vendor-supported fixed release for the deployed branch.
- Verify the affected workflow no longer allows the behavior described in CVE-2026-55574, using a safe regression test or vendor-provided validation method.
- Review logs after remediation for continued exploit attempts, denial-of-service symptoms, suspicious redirects, unauthorized requests, file access, credential exposure, or configuration changes.
- Rerun a Fixnx scan and any product-specific scanner, package audit, device health check, or manual regression test relevant to the affected service.
- Document affected assets, fixed versions, mitigation decisions, validation evidence, and any cleanup or credential rotation performed.
Related categories
Trusted references
FAQ
What is affected by CVE-2026-55574?
vllm should be checked against the vendor advisory and trusted references linked on this page.
What should I fix first?
Start with internet-facing sites, admin panels, login flows, plugins, themes, modules, packages, and systems that process user-controlled input or sensitive data.
How do I confirm the fix worked?
Apply the patched version or mitigation, clear caches where relevant, retest the affected workflow, and run a new Fixnx scan to verify public website exposure signals.
How are Fixnx security risk categories chosen?
Fixnx keeps one canonical risk page and assigns only broad, relevant categories such as ecosystem, technology area, or vulnerability class.