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.
Advisories
Source ID Title
Github GHSA Github GHSA GHSA-7f5h-v6xp-fcq8 Starlette vulnerable to O(n^2) DoS via Range header merging in ``starlette.responses.FileResponse``
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Wed, 29 Oct 2025 11:00:00 +0000

Type Values Removed Values Added
First Time appeared Encode
Encode starlette
Vendors & Products Encode
Encode starlette

Wed, 29 Oct 2025 00:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

threat_severity

Important


Tue, 28 Oct 2025 21:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Tue, 28 Oct 2025 20:30:00 +0000

Type Values Removed Values Added
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.
Title Starlette vulnerable to O(n^2) DoS via Range header merging in starlette.responses.FileResponse
Weaknesses CWE-407
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2025-10-28T20:36:49.189Z

Reserved: 2025-10-20T19:41:22.742Z

Link: CVE-2025-62727

cve-icon Vulnrichment

Updated: 2025-10-28T20:36:44.968Z

cve-icon NVD

Status : Received

Published: 2025-10-28T21:15:40.447

Modified: 2025-10-28T21:15:40.447

Link: CVE-2025-62727

cve-icon Redhat

Severity : Important

Publid Date: 2025-10-28T20:14:53Z

Links: CVE-2025-62727 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2025-10-29T10:57:44Z