Kludex starlette up to 1.0.x on Windows SMB Connection server-side request forgery

Summaryinfo

A vulnerability was found in Kludex starlette up to 1.0.x on Windows. It has been rated as critical. This affects an unknown part of the component SMB Connection Handler. Performing a manipulation results in server-side request forgery. This vulnerability is cataloged as CVE-2026-48818. It is possible to initiate the attack remotely. There is no exploit available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability, which was classified as critical, was found in Kludex starlette up to 1.0.x on Windows. This affects an unknown function of the component SMB Connection Handler. The manipulation with an unknown input leads to a server-side request forgery vulnerability. CWE is classifying the issue as CWE-918. The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

Starlette is a lightweight ASGI framework/toolkit. In versions 1.0.1 and earlier, StaticFiles on Windows is vulnerable to SSRF. An UNC path such as \\attacker.com\share can cause os.path.realpath to initiate an outbound SMB connection before the path is rejected, exposing the service account’s NTLMv2 credentials for offline cracking or relay even though the HTTP response is only a 404. The issue affects default follow_symlink=False deployments, including frameworks built on Starlette such as FastAPI; POSIX systems and follow_symlink=True are unaffected. The issue is fixed in 1.1.0.

It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2026-48818 since 05/22/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. The technical details are unknown and an exploit is not publicly available.

Upgrading to version 1.1.0 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-37773). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Vendor

• Kludex

Name

• starlette

Version

• 1.0

Website

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

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Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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