.NET Core August 2020 Updates – 2.1.21 and 3.1.7

Rahul Bhandari (MSFT)

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


CVE-2020-1597: ASP.NET Core Denial of Service 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 denial of service vulnerability exists when ASP.NET Core improperly handles web requests. An attacker who successfully exploited this vulnerability could cause a denial of service against an ASP.NET Core web application. The vulnerability can be exploited remotely, without authentication.

A remote unauthenticated attacker could exploit this vulnerability by issuing specially crafted requests to the ASP.NET Core application.

The update addresses the vulnerability by correcting how the ASP.NET Core web application handles web requests.

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.

Lifecycle Updates

Ubuntu 19.10 is out of support as of 17th July 2020.

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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  • Jason Baginski 0

    Any chance the hosting bundle could eventually just upgrade the previous hosting bundle? Here’s what’s been happening in my world: See random blog post about a .NET Core update. Download hosting bundle. Install. Our sites are dead. Go to add remove programs, see the x86 and x64 .NET core runtimes are now newer version. New Windows Server Hosting is listed. Old Windows Server Hosting is still listed as well. Uninstall old Windows Server Hosting. Sites still dead. Try repair on new Windows Server Hosting. Sites still dead. Try repair on each core runtime. Sites still dead. Uninstall new Windows Server Hosting and both core runtimes. Reinstall new hosting bundle. Sites alive.

    • Dan Auger 0

      Very similar story here. I really hope that patch releases can be managed via Windows Update once the cutover to .NET 5 happens. We have dozens of servers that need to be manually patched. It’s a huge time suck.

      • Alexey Leonovich 0

        As far as I know .NET Core runtime updating via Microsoft Update channels is planned withing .NET 5 timeframe (and is planned to be backported for .NET Core 3.1) – https://github.com/dotnet/core/issues/5013

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