CVE-2025-62727
High
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.
SeverityHigh
CVSS7.5
Exploit probability—
ProductStarlette
PublishedOct 28, 2025
First seenOct 28, 2025
Weakness typeCWE-407CWE-407
How to fix
Update
- starlette0.49.1 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| starlettePyPI | 0.39.0 ≤ v < 0.49.1 | 0.49.1 |
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