CVE-2025-62727
Starlette vulnerable to O(n^2) DoS via Range header merging in ``starlette.responses.FileResponse``
7.5
HIGH
CVSS 3.1
EPSS 0.07%
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.
How to fix CVE-2025-62727
To remediate CVE-2025-62727, upgrade the affected package to a fixed version below.
- —upgrade to 0.46.1-3+deb13u1 or later
- —upgrade to 0.49.1 or later
Is CVE-2025-62727 being exploited?
Low — EPSS is 0.1%, meaning exploitation activity has not been observed at scale.
Affected packages (2)
- from 0, < 0.46.1-3+deb13u1
- >= 0.39.0, < 0.49.1
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | HIGH7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |