CVE-2025-62727 – Starlette vulnerable to O(n^2) DoS via Range header merging in starlette.responses.FileResponse

CVE ID : CVE-2025-62727

Published : Oct. 28, 2025, 8:14 p.m. | 30 minutes ago

Description : Starlette is a lightweight ASGI framework/toolkit. Prior to 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.

Severity: 0.0 | NA

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