vLLM ReDoS vulnerability in structured outputs regex compilation

# vLLM ReDoS vulnerability in structured outputs regex compilation

https://gcdradar.vercel.app/incidents/vllm-redos-vulnerability-in-structured-outputs-regex-compila · AIR-2026-0811 · closed 2026-07-06

- Lane: Patch now
- Severity: 2 (Disclosed vulnerability)
- Fix status: Fix status unknown
- First reported: 2026-07-06 (happened 2026-07-17)
- AI role: Attack on AI
- Products: vLLM
- CVE ids: CVE-2026-55574
- CVSS: 8.7

## Summary

An unvalidated regex string passed to grammar compiler backends in vLLM can cause a ReDoS denial of service. Crafted patterns cause exponential DFA state-space explosion and hang the inference worker.

## What to do

No action recorded; read the sources below and the vendor's advisory.

## Latest updates

- 2026-07-17: CVE-2026-55574: vLLM: ReDoS via structured_outputs.regex compiled without timeout in xgrammar and outlines backends (https://github.com/advisories/GHSA-rwxx-mrjm-wc2m)
- 2026-07-06: CVE-2026-55574: vLLM is a high-throughput and memory-efficient inference and serving engine for LLMs. (https://nvd.nist.gov/vuln/detail/CVE-2026-55574)

## Sources

- 2026-07-06 NVD: CVE-2026-55574: vLLM is a high-throughput and memory-efficient inference and serving engine for LLMs. https://nvd.nist.gov/vuln/detail/CVE-2026-55574
- 2026-07-17 GitHub Advisory Database: CVE-2026-55574: vLLM: ReDoS via structured_outputs.regex compiled without timeout in xgrammar and outlines backends https://github.com/advisories/GHSA-rwxx-mrjm-wc2m

Verify against the vendor's advisory before changing production. Data CC BY-SA 4.0, https://gcdradar.vercel.app.