Goal Reached Thanks to every supporter — we hit 100%!

Goal: 1000 CNY · Raised: 1359 CNY

100%
Buy Us a Coffee

CVE-2025-62727— Starlette vulnerable to O(n^2) DoS via Range header merging in starlette.responses.FileResponse

Quick assessment

Affected
Kludex starlette
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Starlette是Encode开源的一个轻量级的 ASGI 框架/工具包。非常适合用 Python 构建异步 web 服务。 Starlette 0.49.1之前版本存在安全漏洞，该漏洞源于FileResponse Range解析合并逻辑存在二次时间处理问题，可能导致CPU耗尽和拒绝服务攻击。

CVSS 7.5 · High EPSS 0.80% · P55
Get alerts for future matching vulnerabilities Log in to subscribe

I. Basic Information for CVE-2025-62727

Vulnerability Information
Have questions about the vulnerability? See if Shenlong's analysis helps!
View Shenlong Deep Dive ↗

Although we use advanced large model technology, its output may still contain inaccurate or outdated information.Shenlong tries to ensure data accuracy, but please verify and judge based on the actual situation.

Vulnerability Title
Starlette vulnerable to O(n^2) DoS via Range header merging in starlette.responses.FileResponse
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
算法复杂性
Source: CVE Program / CVE List V5
Vulnerability Title
Starlette 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Starlette是Encode开源的一个轻量级的 ASGI 框架/工具包。非常适合用 Python 构建异步 web 服务。 Starlette 0.49.1之前版本存在安全漏洞，该漏洞源于FileResponse Range解析合并逻辑存在二次时间处理问题，可能导致CPU耗尽和拒绝服务攻击。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Kludex starlette >= 0.39.0, < 0.49.1 -

II. Public POCs for CVE-2025-62727

# POC Description Source Link Shenlong Link
1 Proof of concept of CVE-2025-62727 that can cause denial-of-service in FastAPI (based Starlette <= 0.48.0) https://github.com/ch4n3-yoon/CVE-2025-62727-Demo POC Details
AI-Generated POC Premium
Qwen3.6-35B-A3B · 9473 chars
Pro+ exclusive includes:
Vulnerability reproduction recording (real sandbox build + trigger, exclusive)
In-depth vulnerability mechanism
Trigger conditions & impact
Full executable POC code
Exploit chain & mitigation
POC zip download
100+ AI POC generations per month

III. Intelligence Information for CVE-2025-62727

请登录查看更多情报信息。

Patches & Fixes for CVE-2025-62727 (1)

Vendor Advisories for CVE-2025-62727 (1)

IV. Related Vulnerabilities

Same product: starlette
Same vendor: Kludex
Same weakness: CWE-407

V. Comments for CVE-2025-62727

No comments yet

Leave a comment