CVE-2026-34756

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.

CVSS v3 6.5 MEDIUM

6.5^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 2.8 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required LOW

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://github.com/vllm-project/vllm/commit/b111f8a61f100fdca08706f41f29ef3548de7380	Patch
https://github.com/vllm-project/vllm/pull/37952	Issue Tracking Patch
https://github.com/vllm-project/vllm/security/advisories/GHSA-3mwp-wvh9-7528	Patch Vendor Advisory
https://access.redhat.com/errata/RHSA-2026:36005
https://access.redhat.com/errata/RHSA-2026:36006
https://access.redhat.com/errata/RHSA-2026:57380
https://access.redhat.com/errata/RHSA-2026:57387
https://access.redhat.com/errata/RHSA-2026:57389
https://access.redhat.com/errata/RHSA-2026:57390
https://access.redhat.com/errata/RHSA-2026:59144
https://access.redhat.com/errata/RHSA-2026:59151
https://access.redhat.com/security/cve/CVE-2026-34756
https://bugzilla.redhat.com/show_bug.cgi?id=2455425
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-34756.json

Configurations

Configuration 1 (hide)

cpe:2.3:a:vllm:vllm:*:*:*:*:*:*:*:*

History

No history.

Information

Published : 2026-04-06 16:16

Updated : 2026-08-25 13:18

NVD link : CVE-2026-34756

Mitre link : CVE-2026-34756

CVE.ORG link : CVE-2026-34756

JSON object : View

Products Affected

vllm

vllm

CWE

CWE-770

Allocation of Resources Without Limits or Throttling

CWE-1284

Improper Validation of Specified Quantity in Input

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