Answer in brief
CVE-2026-34756 records a Medium severity (CVSS 6.5) vulnerability in vLLM Affected by Unauthenticated OOM Denial of Service via Unbounded `n` Parameter in OpenAI API Server. The current sources do not mark it as known exploited. The current feed maps vllm-project/vllm (generic), vllm (pip), vllm (pypi). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 6.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps vllm-project/vllm (generic), vllm (pip), vllm (pypi). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| vllm-project/vllmgeneric | >= 0.1.0, < 0.19.0 | Not reported |
| vllmpip | >=0.1.0,<0.19.0 | 0.19.0 |
| vllmpypi | >=0.1.0 <0.19.0 | 0.19.0 |
Published upstream
Apr 6, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 20, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jul 7, 2026
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.
Quoted source text, attributed separately from HOL analysis.