CVE-2025-62727
October 28, 2025
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.
Affected Packages
starlette (CONDA):
Affected version(s) >=0.4.2 <0.49.1Fix Suggestion:
Update to version 0.49.1https://github.com/Kludex/starlette.git (GITHUB):
Affected version(s) >=0.1.0 <0.49.1Fix Suggestion:
Update to version 0.49.1starlette (PYTHON):
Affected version(s) >=0.39.0 <0.49.1Fix Suggestion:
Update to version 0.49.1Related Resources (6)
Do you need more information?
Contact UsCVSS v4
Base Score:
8.7
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
NONE
Vulnerable System Confidentiality
NONE
Vulnerable System Integrity
NONE
Vulnerable System Availability
HIGH
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
7.5
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Weakness Type (CWE)
EPSS
Base Score:
0.5
