id: PYSEC-2026-2298
published: "2026-04-06T16:16:36.610Z"
modified: "2026-07-13T05:52:25.124808Z"
aliases:
- CVE-2026-34756
- GHSA-3mwp-wvh9-7528
details: 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.
affected:
- package:
    name: vllm
    ecosystem: PyPI
    purl: pkg:pypi/vllm
  ranges:
  - type: ECOSYSTEM
    events:
    - introduced: 0.1.0
    - fixed: 0.19.0
  versions:
  - 0.1.0
  - 0.1.1
  - 0.1.2
  - 0.1.3
  - 0.1.4
  - 0.1.5
  - 0.1.6
  - 0.1.7
  - 0.10.0
  - 0.10.1
  - 0.10.1.1
  - 0.10.2
  - 0.11.0
  - 0.11.1
  - 0.11.2
  - 0.12.0
  - 0.13.0
  - 0.14.0
  - 0.14.1
  - 0.15.0
  - 0.15.1
  - 0.16.0
  - 0.17.0
  - 0.17.1
  - 0.18.0
  - 0.18.1
  - 0.2.0
  - 0.2.1
  - 0.2.1.post1
  - 0.2.2
  - 0.2.3
  - 0.2.4
  - 0.2.5
  - 0.2.6
  - 0.2.7
  - 0.3.0
  - 0.3.1
  - 0.3.2
  - 0.3.3
  - 0.4.0
  - 0.4.0.post1
  - 0.4.1
  - 0.4.2
  - 0.4.3
  - 0.5.0
  - 0.5.0.post1
  - 0.5.1
  - 0.5.2
  - 0.5.3
  - 0.5.3.post1
  - 0.5.4
  - 0.5.5
  - 0.6.0
  - 0.6.1
  - 0.6.1.post1
  - 0.6.1.post2
  - 0.6.2
  - 0.6.3
  - 0.6.3.post1
  - 0.6.4
  - 0.6.4.post1
  - 0.6.5
  - 0.6.6
  - 0.6.6.post1
  - 0.7.0
  - 0.7.1
  - 0.7.2
  - 0.7.3
  - 0.8.0
  - 0.8.1
  - 0.8.2
  - 0.8.3
  - 0.8.4
  - 0.8.5
  - 0.8.5.post1
  - 0.9.0
  - 0.9.0.1
  - 0.9.1
  - 0.9.2
  ecosystem_specific: {}
references:
- type: WEB
  url: https://access.redhat.com/security/cve/CVE-2026-34756
- type: WEB
  url: https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-34756.json
- type: ADVISORY
  url: https://access.redhat.com/errata/RHSA-2026:36005
- type: ADVISORY
  url: https://access.redhat.com/errata/RHSA-2026:36006
- type: REPORT
  url: https://bugzilla.redhat.com/show_bug.cgi?id=2455425
- type: FIX
  url: https://github.com/vllm-project/vllm/commit/b111f8a61f100fdca08706f41f29ef3548de7380
- type: FIX
  url: https://github.com/vllm-project/vllm/pull/37952
- type: FIX
  url: https://github.com/vllm-project/vllm/security/advisories/GHSA-3mwp-wvh9-7528
severity:
- type: CVSS_V3
  score: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H