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GHSA-3mwp-wvh9-7528: vLLM: Unauthenticated OOM Denial of Service via Unbounded `n` Parameter in OpenAI API Server

OSV AI package advisories · observation · Apr 3, 2026 · UTC

### Summary 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. ### Details The root cause of this vulnerability lies in

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recordType
vulnerability
status
active
evidenceStatus
reported
region
Global

Evidence & attribution

First collected: 2026-09-20T22:31:48.298Z. This is not the publication date.