CVE-2026-34756
MEDIUM EPSS 21.0%
Published Apr 6, 20262mo ago · Modified Jun 17, 20262w ago
6.5 CVSS 3.1
Published Apr 6, 2026 2mo ago
Last Modified Jun 17, 2026 2w ago
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.
CVSS Details
Base Score
Exploitability
Impact
Vector string
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Attack Vector Network
Attack Complexity Low
Privileges Required Low
User Interaction None
Scope Unchanged
Confidentiality None
Integrity None
Availability High
Threat Intelligence
EPSS Exploit Probability
21.0% percentile
Exploit & Patch Status
No Known Exploit
Patch Available
Weaknesses 1
CWE-770
Affected Products 1
| Vendor | Product | Version | Range |
|---|---|---|---|
| vllm | vllm | * | ≥0.1.0 – <0.19.0 |
References 3
- github.com https://github.com/vllm-project/vllm/commit/b111f8a61f100fdca08706f41f29ef3548de7380
- github.com https://github.com/vllm-project/vllm/pull/37952
- github.com https://github.com/vllm-project/vllm/security/advisories/GHSA-3mwp-wvh9-7528
Remediation
- github.com https://github.com/vllm-project/vllm/commit/b111f8a61f100fdca08706f41f29ef3548de7380
- github.com https://github.com/vllm-project/vllm/pull/37952
- github.com https://github.com/vllm-project/vllm/security/advisories/GHSA-3mwp-wvh9-7528