October 13, 2020-KB4578966 Cumulative Update for .NET Framework 3.5 and 4.7.2 for Windows 10, version 1809 and Windows Server, version 2019

Applies to: .NET Framework

Summary


An information disclosure vulnerability exists when the .NET Framework improperly handles objects in memory. An attacker who successfully exploited the vulnerability could disclose contents of an affected system's memory. To exploit the vulnerability, an authenticated attacker would need to run a specially crafted application. The update addresses the vulnerability by correcting how the .NET Framework handles objects in memory.

To learn more about the vulnerabilities, go to the following Common Vulnerabilities and Exposures (CVE).

Known issues in this security update


Symptoms
After you apply this October 13, 2020 Security and Quality Rollup for .NET Framework 4.8, some ASP.Net applications fail during precompilation. The error message that you receive will likely contain the words “Error ASPCONFIG.”

Cause
An invalid configuration state in either the “sessionState,” “anonymouseIdentification,” or “authentication/forms” sections of “System.web” configuration. This might occur during build-and-publish routines if configuration transformations leave the Web.config file in an intermediate state for precompilation.

Workaround
Customers who observe new unexpected failures or functional issues can implement an application setting by adding (or merging) the following code to the application configuration file. Setting either “true” or “false” will avoid the issue. However, we recommend that you set this value to “true” for sites that do not rely on cookieless features.

<?xml version="1.0" encoding="utf-8" ?><configuration>      <appSettings>          <add key=”aspnet:DisableAppPathModifier” value=”true” />     </appSettings></configuration>

How to get this update


Install this update

Release Channel Available Next Step
Windows Update and Microsoft Update Yes None. This update will be downloaded and installed automatically from Windows Update.
Microsoft Update Catalog Yes To get the standalone package for this update, go to the Microsoft Update Catalog website.
Windows Server Update Services (WSUS) Yes

This update will automatically sync with WSUS if you configure Products and Classifications as follows:

Product:Windows 10, version 1809 and Windows Server, version 2019

Classification: Security Updates

File information

For a list of the files that are provided in this update, download the file information for cumulative update .

Additional information about this update


The following articles contain additional information about this update as it relates to individual product versions.
  • 4579976 Description of the Cumulative Update for .NET Framework 3.5 and 4.7.2 for Windows 10 Version 1809 for ARM64 (KB4579976)

Information about protection and security