CVE-2025-62727

HIGH7.5

Starlette vulnerable to O(n^2) DoS via Range header merging in starlette.responses.FileResponse

Published Oct 28, 2025

Modified 4 months ago

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.

References

WEB

https://github.com/Kludex/starlette/commit/4ea6e22b489ec388d6004cfbca52dd5b147127c5

WEB

https://github.com/Kludex/starlette/commit/69ed26a85956ef4bd0161807eb27abf49be7cd3c

WEB

https://github.com/Kludex/starlette/releases/tag/0.49.1

DETECTION

https://github.com/Kludex/starlette/security/advisories/GHSA-7f5h-v6xp-fcq8

ADVISORY

https://www.cve.org/CVERecord?id=CVE-2025-62727

CVSS Analysis