.NET Core September 2020 Updates – 2.1.22 and 3.1.8

Rahul Bhandari (MSFT)

Today, we are releasing the .NET Core September 2020 Update. These updates contain security and reliability fixes. See the individual release notes for details on updated packages.


CVE-2020-1045: ASP.NET Core Security Feature Bypass Vulnerability

Microsoft is releasing this security advisory to provide information about a vulnerability in ASP.NET Core. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability.

A security feature bypass vulnerability exists in the way Microsoft ASP.NET Core parses encoded cookie names.
The ASP.NET Core cookie parser decodes entire cookie strings which could allow a malicious attacker to set a second cookie with the name being percent encoded.
The security update addresses the vulnerability by fixing the way the ASP.NET Core cookie parser handles encoded names.

Getting the Update

See the .NET Core release notes for details on the release, including issues fixed and affected packages. 

The latest .NET Core updates are available on the .NET Core download page.

Docker Images

.NET Docker images have been updated for today’s release. The following repos have been updated.

Note: You must pull updated .NET Core container images to get this update, with either docker pull or docker build --pull.

Visual Studio

This update will be included in a future update of Visual Studio.

Each version of Visual studio is only supported with a given version of the .NET Core SDK. Visual Studio version information is included in the .NET Core SDK download pages and release notes.If you are not using Visual Studio, we recommend using the latest SDK release.



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  • Christopher Mire 0

    I still don’t see 3.1.7 runtime listed under https://{name}.scm.azurewebsites.net/api/diagnostics/runtime, which was supposed to roll out in August. How long do these rollouts take?

    • Mike M 0


      What is the ETA for .NET Core 3.1.8 runtime for Azure Apps?

      • Rahul Bhandari (MSFT)Microsoft employee 0

        The 3.1.8 update is available on Azure Apps.

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