{"id":"PYSEC-2026-2021","summary":"vllm API endpoints vulnerable to Denial of Service Attacks","details":"### Summary\nA Denial of Service (DoS) vulnerability can be triggered by sending a single HTTP GET request with an extremely large header to an HTTP endpoint. This results in server memory exhaustion, potentially leading to a crash or unresponsiveness. The attack does not require authentication, making it exploitable by any remote user.\n\n### Details\nThe vulnerability leverages the abuse of HTTP headers. By setting a header such as `X-Forwarded-For` to a very large value like `(\"A\" * 5_800_000_000)`, the server's HTTP parser or application logic may attempt to load the entire request into memory, overwhelming system resources.\n\n### Impact\n_What kind of vulnerability is it? Who is impacted?_\nType of vulnerability: Denial of Service (DoS)\n\n### Resolution\nUpgrade to a version of vLLM that includes appropriate HTTP limits by deafult, or use a proxy in front of vLLM which provides protection against this issue.","aliases":["CVE-2025-48956","GHSA-rxc4-3w6r-4v47"],"modified":"2026-07-07T17:48:17.626607221Z","published":"2026-07-07T16:03:01.559740Z","references":[{"type":"WEB","url":"https://github.com/vllm-project/vllm/security/advisories/GHSA-rxc4-3w6r-4v47"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-48956"},{"type":"WEB","url":"https://github.com/vllm-project/vllm/pull/23267"},{"type":"WEB","url":"https://github.com/vllm-project/vllm/commit/d8b736f913a59117803d6701521d2e4861701944"},{"type":"PACKAGE","url":"https://github.com/vllm-project/vllm"},{"type":"PACKAGE","url":"https://pypi.org/project/vllm"},{"type":"ADVISORY","url":"https://github.com/advisories/GHSA-rxc4-3w6r-4v47"}],"affected":[{"package":{"name":"vllm","ecosystem":"PyPI","purl":"pkg:pypi/vllm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0.1.0"},{"fixed":"0.10.1.1"}]}],"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","0.2.0","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"],"database_specific":{"source":"https://github.com/pypa/advisory-database/blob/main/vulns/vllm/PYSEC-2026-2021.yaml"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}]}