{"id":"CVE-2026-34756","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.","aliases":["GHSA-3mwp-wvh9-7528"],"modified":"2026-07-09T03:51:25.408116628Z","published":"2026-04-06T15:40:03.448Z","related":["CGA-hp52-rrwx-fx5r"],"database_specific":{"cwe_ids":["CWE-770"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/34xxx/CVE-2026-34756.json","cna_assigner":"GitHub_M"},"references":[{"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":"ADVISORY","url":"https://access.redhat.com/security/cve/CVE-2026-34756"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/34xxx/CVE-2026-34756.json"},{"type":"ADVISORY","url":"https://github.com/vllm-project/vllm/security/advisories/GHSA-3mwp-wvh9-7528"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-34756"},{"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"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/vllm-project/vllm","events":[{"introduced":"67d96c29fba9b72cb4c4edbc26211c208a00ebdd"},{"fixed":"2a69949bdadf0e8942b7a1619b229cb475beef20"},{"fixed":"b111f8a61f100fdca08706f41f29ef3548de7380"}],"database_specific":{"cpe":"cpe:2.3:a:vllm:vllm:*:*:*:*:*:*:*:*","extracted_events":[{"introduced":"0.1.0"},{"fixed":"0.19.0"}],"source":["CPE_RANGE","REFERENCES"]}}],"versions":["v0.19.0rc1","v0.19.0rc0","v0.18.1rc0","v0.17.2rc0","v0.18.0rc0","v0.17.1rc0","v0.17.0rc0","v0.16.0rc1","v0.15.2rc0","v0.16.0rc0","v0.15.0rc1","v0.14.0rc1","v0.14.0rc0","v0.13.0rc1","v0.11.1","v0.11.1rc6","v0.11.1rc5","v0.11.1rc4","v0.11.1rc3","v0.11.1rc2","v0.11.1rc1","v0.11.1rc0","v0.11.0rc1","v0.10.2rc2","v0.10.2rc1","v0.10.1rc1","v0.10.0rc2","v0.10.0","v0.10.0rc1","v0.9.2rc1","v0.9.1rc2","v0.9.1","v0.9.1rc1","v0.9.0","v0.8.4","v0.8.3rc1","v0.8.2","v0.8.1","v0.8.0rc2","v0.8.0rc1","v0.7.3","v0.7.2","v0.7.1","v0.7.0","v0.6.6.post1","v0.6.6","v0.6.5","v0.6.4.post1","v0.6.4","v0.6.3.post1","v0.6.3","v0.6.2","v0.6.1.post2","v0.6.1.post1","v0.6.1","v0.6.0","v0.5.5","v0.5.4","v0.5.3.post1","v0.5.3","v0.5.2","v0.5.1","v0.5.0.post1","v0.5.0","v0.4.3","v0.4.2","v0.4.1","v0.4.0.post1","v0.4.0","v0.3.3","v0.3.2","v0.3.1","v0.3.0","v0.2.7","v0.2.6","v0.2.5","v0.2.4","v0.2.3","v0.2.2","v0.2.1","v0.2.0","v0.1.7","v0.1.6","v0.1.5","v0.1.4","v0.1.3","v0.1.2","v0.1.1","v0.1.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-34756.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"}]}