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Description

vLLM is an inference and serving engine for large language models (LLMs). From 0.1.0 to before 0.19.0, a Denial of Service vulnerability exists in the vLLM OpenAI-compatible API server. Due to the lack of an upper bound validation on the n parameter in the ChatCompletionRequest and CompletionRequest Pydantic models, an unauthenticated attacker can send a single HTTP request with an astronomically large n value. This completely blocks the Python asyncio event loop and causes immediate Out-Of-Memory crashes by allocating millions of request object copies in the heap before the request even reaches the scheduling queue. This vulnerability is fixed in 0.19.0.

PUBLISHED Reserved 2026-03-30 | Published 2026-04-06 | Updated 2026-04-07 | Assigner GitHub_M




MEDIUM: 6.5CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Problem types

CWE-770: Allocation of Resources Without Limits or Throttling

Product status

>= 0.1.0, < 0.19.0
affected

References

github.com/...t/vllm/security/advisories/GHSA-3mwp-wvh9-7528

github.com/vllm-project/vllm/pull/37952

github.com/...ommit/b111f8a61f100fdca08706f41f29ef3548de7380

cve.org (CVE-2026-34756)

nvd.nist.gov (CVE-2026-34756)

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