Starlette vulnerable to O(n^2) DoS via Range header merging in starlette.responses.FileResponse

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2025-62727
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2025-10-28 21:15:40 UTC
Updated2026-10-08 11:10:00 UTC
DescriptionStarlette 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.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Problem Types: CWE-407 | CWE-407 CWE-407: Inefficient Algorithmic Complexity

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1CNADECLARED7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Kludex Starlette affected >= 0.39.0, < 0.49.1 Not specified

References

ReferenceSourceLinkTags
github.com/Kludex/starlette/releases/tag/0.49.1 [email protected] github.com
github.com/Kludex/starlette/security/advisories/GHSA-7f5h-v6xp-fcq8 134c704f-9b21-4f2e-91b3-4a467353bcc0 github.com
github.com/Kludex/starlette/commit/69ed26a85956ef4bd0161807eb27abf49be7cd3c [email protected] github.com
github.com/Kludex/starlette/commit/4ea6e22b489ec388d6004cfbca52dd5b147127c5 [email protected] github.com
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