Vulnerability Description
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 Score
HIGH
Related Weaknesses (CWE)
References
- https://github.com/Kludex/starlette/commit/4ea6e22b489ec388d6004cfbca52dd5b14712
- https://github.com/Kludex/starlette/commit/69ed26a85956ef4bd0161807eb27abf49be7c
- https://github.com/Kludex/starlette/releases/tag/0.49.1
- https://github.com/Kludex/starlette/security/advisories/GHSA-7f5h-v6xp-fcq8
- https://github.com/Kludex/starlette/security/advisories/GHSA-7f5h-v6xp-fcq8
FAQ
What is CVE-2025-62727?
CVE-2025-62727 is a vulnerability with a CVSS score of 7.5 (HIGH). 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-tim...
How severe is CVE-2025-62727?
CVE-2025-62727 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2025-62727?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.