{"id":"CVE-2025-62727","published":"2025-10-28T20:14:53Z","modified":"2025-11-04T17:41:42Z","title":"Starlette vulnerable to O(n^2) DoS via Range header merging in starlette.responses.FileResponse","vendor":"Kludex","product":"starlette","tier":"tail","description":{"text":"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.","provenance":"source","from":"CVE.org"},"cvss":{"score":7.5,"severity":"HIGH","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","provenance":"source","from":"CVE.org CNA"},"epss":{"score":0.008,"percentile":0.56436,"provenance":"source"},"cwes":[{"id":"CWE-407","name":"Inefficient Algorithmic Complexity"}],"references":[{"url":"https://github.com/Kludex/starlette/security/advisories/GHSA-7f5h-v6xp-fcq8","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/Kludex/starlette/commit/4ea6e22b489ec388d6004cfbca52dd5b147127c5","tags":["x_refsource_MISC"]},{"url":"https://github.com/Kludex/starlette/commit/69ed26a85956ef4bd0161807eb27abf49be7cd3c","tags":["x_refsource_MISC"]},{"url":"https://github.com/Kludex/starlette/releases/tag/0.49.1","tags":["x_refsource_MISC"]}],"priority":{"score":21.5,"factors":[{"name":"EPSS percentile","points":11.29},{"name":"Public exploit code","points":5.0},{"name":"CVSS severity","points":5.25}]},"exploitSources":{"pocGithub":{"count":1,"skipped":0,"earliest":"2025-10-28","earliestUrl":"https://github.com/ch4n3-yoon/CVE-2025-62727-Demo","repos":[{"name":"ch4n3-yoon/CVE-2025-62727-Demo","url":"https://github.com/ch4n3-yoon/CVE-2025-62727-Demo","stars":1,"created":"2025-10-28"}]},"first":{"date":"2025-10-28","source":"PoC-in-GitHub","url":"https://github.com/ch4n3-yoon/CVE-2025-62727-Demo"},"provenance":"source"},"vendorSlug":"kludex","affectedVersions":[{"vendor":"Kludex","product":"starlette","versions":[">= 0.39.0, < 0.49.1"]}],"affected":[{"ecosystem":"PyPI","package":"starlette","vulnerableRanges":[">=0.39.0, <0.49.1"],"patched":["0.49.1"],"from":["GHSA-7f5h-v6xp-fcq8","PYSEC-2026-1942"],"provenance":"source"}],"euvd":{"id":"EUVD-2025-36555","exploited":false,"provenance":"source"}}