Vulnerability Intelligence Report
Starlette vulnerable to O(n^2) DoS via Range header merging in starlette.responses.FileResponse
CVE-2025-62727
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.
No Active Exploit Signals
CVSS Base Score
7.5
HIGH
Exploitability:3.9
Impact Score:3.6
EPSS Probability:0.60%
Executive Threat Verdict
Evaluating...
Evaluating Threat Landscape...
Assessing known weaponization, exploitation telemetry, and federal advisories.
Attack Surface
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Authentication
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Weaponization
—
SSVC Action
—
Weaknesses (CWE)
CWE-407 ↗CWE-407: Inefficient Algorithmic Complexity
Affected Products & Versions
| Vendor | Product | Affected Versions |
|---|---|---|
| Kludex | starlette | >= 0.39.0, < 0.49.1 (affected) |
References & Technical Advisories
No reference links found.
Threat Intelligence Signals
EPSS Score
0.597%
GitHub Advisory
Identity & Timeline
| Status | PUBLISHED |
| Assigning Authority | GitHub, Inc. · Vendor · USA |
| Reserved | 2025-10-20T19:41:22 |
| Published | 2025-10-28T20:14:53 |
| Last Updated | 2025-11-04T17:41:42 |
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