Kludex starlette up to 0.49.0 FileResponse Range Parser algorithmic complexity

Summaryinfo

A vulnerability, which was classified as problematic, has been found in Kludex starlette up to 0.49.0. This issue affects some unknown processing of the component FileResponse Range Parser. Performing a manipulation results in algorithmic complexity. This vulnerability is known as CVE-2025-62727. Remote exploitation of the attack is possible. No exploit is available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic has been found in Kludex starlette up to 0.49.0. This affects an unknown functionality of the component FileResponse Range Parser. The manipulation with an unknown input leads to a algorithmic complexity vulnerability. CWE is classifying the issue as 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. This is going to have an impact on availability. The summary by CVE is:

Starlette is a lightweight ASGI framework/toolkit. Prior to 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.

The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2025-62727 since 10/20/2025. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Neither technical details nor an exploit are publicly available. MITRE ATT&CK project uses the attack technique T1499 for this issue.

The vulnerability scanner Nessus provides a plugin with the ID 271968 (Linux Distros Unpatched Vulnerability : CVE-2025-62727), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 0.49.1 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (271968). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Vendor

• Kludex

Name

• starlette

Version

• 0.1
• 0.2
• 0.3
• 0.4
• 0.5
• 0.6
• 0.7
• 0.8
• 0.9
• 0.10
• 0.11
• 0.12
• 0.13
• 0.14
• 0.15
• 0.16
• 0.17
• 0.18
• 0.19
• 0.20
• 0.21
• 0.22
• 0.23
• 0.24
• 0.25
• 0.26
• 0.27
• 0.28
• 0.29
• 0.30
• 0.31
• 0.32
• 0.33
• 0.34
• 0.35
• 0.36
• 0.37
• 0.38
• 0.39
• 0.40
• 0.41
• 0.42
• 0.43
• 0.44
• 0.45
• 0.46
• 0.47
• 0.48
• 0.49.0

Website

• Product: https://github.com/Kludex/starlette/

CPE 2.3info

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Entryinfo

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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