CVE-2025-62727
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-10-28

Last updated on: 2025-11-04

Assigner: GitHub, Inc.

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.
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Meta Information
Published
2025-10-28
Last Modified
2025-11-04
Generated
2026-06-16
AI Q&A
2025-10-28
EPSS Evaluated
2026-06-15
NVD
CVE-2025-62727
Affected Vendors & Products
Showing 2 associated CPEs
Vendor Product Version / Range
kludex starlette 0.49.0
kludex starlette 0.49.1
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-407 An algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an attacker, typically using crafted manipulations that ensure that the worst case is being reached.
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Executive Summary

This vulnerability in Starlette versions prior to 0.49.1 allows an unauthenticated attacker to send a specially crafted HTTP Range header that causes the FileResponse component to perform quadratic-time processing during Range parsing and merging. This excessive processing leads to high CPU usage per request, potentially causing denial-of-service conditions on endpoints serving files.

Impact Analysis

The vulnerability can lead to denial-of-service (DoS) attacks by exhausting CPU resources on servers running vulnerable versions of Starlette when handling file-serving endpoints. This can make the affected services unavailable to legitimate users.

Mitigation Strategies

Upgrade Starlette to version 0.49.1 or later, as this version contains the fix for the vulnerability. Until the upgrade can be applied, consider restricting or disabling endpoints serving files using FileResponse or StaticFiles to prevent exploitation.

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