CVE-2026-34756

See a problem?
Please try reporting it to the source first.

Source

https://cve.org/CVERecord?id=CVE-2026-34756

Import Source

https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-34756.json

JSON Data

https://api.osv.dev/v1/vulns/CVE-2026-34756

Aliases

Downstream

CGA (9)

Published

2026-04-06T15:40:03Z

Modified

2026-10-28T02:30:55Z

Severity

6.5 (Medium) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H CVSS Calculator

Summary

vLLM Affected by Unauthenticated OOM Denial of Service via Unbounded `n` Parameter in OpenAI API Server

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.

Database specific

{
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
        "CWE-770"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/34xxx/CVE-2026-34756.json"
}

References

Affected packages

Git / github.com/vllm-project/vllm

Affected ranges

Type

GIT

Repo

https://github.com/vllm-project/vllm

Events

Introduced

67d96c29fba9b72cb4c4edbc26211c208a00ebdd

Fixed

2a69949bdadf0e8942b7a1619b229cb475beef20

Fixed

b111f8a61f100fdca08706f41f29ef3548de7380

Database specific

Show details

{
    "extracted_events": [
        {
            "cpe": "cpe:2.3:a:vllm:vllm:*:*:*:*:*:*:*:*",
            "range": [
                {
                    "introduced": "0.1.0"
                },
                {
                    "fixed": "0.19.0"
                }
            ],
            "source": "CPE_RANGE"
        },
        {
            "range": [
                {
                    "fixed": "b111f8a61f100fdca08706f41f29ef3548de7380"
                }
            ],
            "source": "REFERENCES_COMMIT"
        }
    ]
}

Affected versions

v0.*

v0.1.0

v0.1.1

v0.1.2

v0.1.3

v0.1.4

v0.1.5

v0.1.6

v0.1.7

v0.10.0

v0.10.0rc1

v0.10.0rc2

v0.10.1rc1

v0.10.2rc1

v0.10.2rc2

v0.11.0rc1

v0.11.1

v0.11.1rc0

v0.11.1rc1

v0.11.1rc2

v0.11.1rc3

v0.11.1rc4

v0.11.1rc5

v0.11.1rc6

v0.13.0rc1

v0.14.0rc0

v0.14.0rc1

v0.15.0rc1

v0.15.2rc0

v0.16.0rc0

v0.16.0rc1

v0.17.0rc0

v0.17.1rc0

v0.17.2rc0

v0.18.0rc0

v0.18.1rc0

v0.2.0

v0.2.1

v0.2.2

v0.2.3

v0.2.4

v0.2.5

v0.2.6

v0.2.7

v0.3.0

v0.3.1

v0.3.2

v0.3.3

v0.4.0

v0.4.0.post1

v0.4.1

v0.4.2

v0.4.3

v0.5.0

v0.5.0.post1

v0.5.1

v0.5.2

v0.5.3

v0.5.3.post1

v0.5.4

v0.5.5

v0.6.0

v0.6.1

v0.6.1.post1

v0.6.1.post2

v0.6.2

v0.6.3

v0.6.3.post1

v0.6.4

v0.6.4.post1

v0.6.5

v0.6.6

v0.6.6.post1

v0.7.0

v0.7.1

v0.7.2

v0.7.3

v0.8.0rc1

v0.8.0rc2

v0.8.1

v0.8.2

v0.8.3rc1

v0.8.4

v0.9.0

v0.9.1

v0.9.1rc1

v0.9.1rc2

v0.9.2rc1

Database specific

source

"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-34756.json"