Medium · published June 20, 2026
vLLM versions >= 0.6.3 and < 0.9.0 contain multiple regular expression denial of service (ReDoS) vulnerabilities. Several regex patterns — in vllm/lora/utils.py, the phi4mini tool parser, and the OpenAI-compatible serving chat endpoint — are susceptible to catastrophic backtracking. An attacker submitting crafted input with nested or repeated structures can trigger severe CPU consumption and performance degradation, resulting in denial of service.
| Product | Versions | Fixed in |
|---|---|---|
| vllm/vllm | ≥ 0.6.3, < 0.9.0 | 0.9.0 |