{"id":"CVE-2025-62727","aliases":["GHSA-7f5h-v6xp-fcq8","PYSEC-2026-1942"],"url":"https://o3.security/vulnerability/CVE-2025-62727","summary":"Starlette vulnerable to O(n^2) DoS via Range header merging in starlette.responses.FileResponse","details":"Starlette is a lightweight ASGI framework/toolkit. Starting in version 0.39.0 and prior to version 0.49.1 , an unauthenticated attacker can send a crafted HTTP Range header that triggers quadratic-time processing in Starlette's FileResponse Range parsing/merging logic. This enables CPU exhaustion per request, causing denial‑of‑service for endpoints serving files (e.g., StaticFiles or any use of FileResponse). This vulnerability is fixed in 0.49.1.","published":"2025-10-28T20:14:53.655Z","modified":"2026-08-12T03:51:48.542248399Z","cvss":{"score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},"epss":{"score":0.00638,"percentile":0.47825,"asOf":"2026-08-24"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"starlette","fixedVersion":"0.49.1"}],"fix":{"url":"https://github.com/Kludex/starlette/commit/4ea6e22b489ec388d6004cfbca52dd5b147127c5","label":"Kludex/starlette@4ea6e22"},"references":[{"type":"WEB","url":"https://github.com/Kludex/starlette/releases/tag/0.49.1"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/62xxx/CVE-2025-62727.json"},{"type":"ADVISORY","url":"https://github.com/Kludex/starlette/security/advisories/GHSA-7f5h-v6xp-fcq8"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-62727"},{"type":"FIX","url":"https://github.com/Kludex/starlette/commit/4ea6e22b489ec388d6004cfbca52dd5b147127c5"},{"type":"FIX","url":"https://github.com/Kludex/starlette/commit/69ed26a85956ef4bd0161807eb27abf49be7cd3c"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:48.542248399Z"}}