CVE-2025-62727highCWE-407

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

21Vexday Risk Score

No sign of exploitation. No public exploitation artifact known so far.

ssvc Trackcvss 7.5epss 0.6%

exploitation probability

0.6%top 53% of all CVEs

observed exploitation

nono source reports it

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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

Kludex · starlette

References

https://github.com/Kludex/starlette/commit/4ea6e22b489ec388d6004cfbca52dd5b147127c5 https://github.com/Kludex/starlette/commit/69ed26a85956ef4bd0161807eb27abf49be7cd3c https://github.com/Kludex/starlette/releases/tag/0.49.1 https://github.com/Kludex/starlette/security/advisories/GHSA-7f5h-v6xp-fcq8