Security Only Update for .NET Framework 3.5, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8 for Windows 8.1 and Windows Server 2012 R2 (KB4566468)

**Applies to:**Microsoft .NET Framework 3.5 Microsoft .NET Framework 4.5.2 Microsoft .NET Framework 4.6 Microsoft .NET Framework 4.6.1 Microsoft .NET Framework 4.6.2 Microsoft .NET Framework 4.7 Microsoft .NET Framework 4.7.1 Microsoft .NET Framework 4.7.2 Microsoft .NET Framework 4.8

Summary

A remote code execution vulnerability exists in .NET Framework when the software fails to check the source markup of XML file input. An attacker who successfully exploited the vulnerability could run arbitrary code in the context of the process responsible for deserialization of the XML content. To exploit this vulnerability, an attacker could upload a specially crafted document to a server utilizing an affected product to process content. The security update addresses the vulnerability by correcting how .NET Framework validates the source markup of XML content. This security update affects how .NET Framework’s System.Data.DataTable and System.Data.DataSet types read XML-serialized data. Most .NET Framework applications will not experience any behavioral change after the update is installed. For more information on how the update affects .NET Framework, including examples of scenarios which may be affected, please see the DataTable and DataSet security guidance document at <https://go.microsoft.com/fwlink/?linkid=2132227&gt;. To learn more about the vulnerabilities, go to the following Common Vulnerabilities and Exposures (CVE).

• CVE-2020-1147
  Important

• As a reminder to advanced IT administrators, updates to .NET Framework 3.5 for Windows 8.1 and Windows Server 2012 R2 should only be applied on systems where .NET Framework 3.5 is present and enabled. Customers who attempt to pre-install updates to .NET Framework 3.5 to offline images that do not contain the .NET Framework 3.5 product enabled will expose these systems to failures to enable .NET Framework 3.5 after the systems are online. For more extensive information about deploying .NET Framework 3.5, see Microsoft .NET Framework 3.5 Deployment Considerations.

• All updates for Windows 8.1, Windows RT 8.1, and Windows Server 2012 R2 require that update KB 2919355 is installed. We recommend that you install update KB 2919355 on your Windows 8.1-based, Windows RT 8.1-based, or Windows Server 2012 R2-based computer so that you receive updates in the future.

• If you install a language pack after you install this update, you must reinstall this update. Therefore, we recommend that you install any language packs that you need before you install this update. For more information, see Add language packs to Windows.

Known Issues

Symptoms:After you apply this update, some applications experience aTypeInitializationExceptionexception when they try to deserializeSystem.Data.DataSetorSystem.Data.DataTable instances from the XML within a SQL CLR stored procedure. The stack trace for this exception appears as follows:System.TypeInitializationException: The type initializer for ‘Scope’ threw an exception. —> System.IO.FileNotFoundException: Could not load file or assembly ‘System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a’ or one of its dependencies. The system cannot find the file specified.
at System.Data.TypeLimiter.Scope.IsTypeUnconditionallyAllowed(Type type)
at System.Data.TypeLimiter.Scope.IsAllowedType(Type type)
at System.Data.TypeLimiter.EnsureTypeIsAllowed(Type type, TypeLimiter capturedLimiter)**Resolution:**Install the latest version of this update that was released on October 13th, 2020.

Additional information about this update

The following articles contain additional information about this update as it relates to individual product versions.

• 4565580 Description of the Security Only Update for .NET Framework 3.5 for Windows 8.1 and Windows Server 2012 R2 (KB4565580)
• 4565581 Description of the Security Only Update for .NET Framework 4.5.2 for Windows 8.1 and Windows Server 2012 R2 (KB4565581)
• 4565585 Description of the Security Only Update for .NET Framework 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2 for Windows 8.1 and Windows Server 2012 R2 (KB4565585)
• 4565588 Description of the Security Only Update for .NET Framework 4.8 for Windows 8.1 and Windows Server 2012 R2 (KB4565588)

Information about protection and security

• Protect yourself online: Windows Security support
• Learn how we guard against cyber threats: Microsoft Security