July 9, 2019 — KB4506991 Cumulative Update for .NET Framework 3.5 and 4.8 for Windows 10, version 1903
Microsoft .NET Framework 3.5 and 4.8
A remote code execution vulnerability exists in .NET software if the software fails to check the source markup of a file. An Authentication Bypass vulnerability exists in WCF and WIF that lets SAML tokens be signed by using arbitrary symmetric keys. This vulnerability enables an attacker to impersonate another user. The vulnerability exists in WCF, WIF 3.5, and later in .NET Framework, WIF 1.0 component in Windows, WIF Nuget package, and WIF implementation in SharePoint. An information disclosure vulnerability exists if Exchange and Azure Active Directory enable entities to be created even though they have Display Names that contain non-printable characters.
To learn more about the vulnerabilities, go to the following Common Vulnerabilities and Exposures (CVE):
Known issues in this update
Microsoft is not currently aware of any issues in this update.
How to get this update
Install this update
To download and install this update, go to Settings, Update & Security, Windows Update, and then select Check for updates.
This update will be downloaded and installed automatically from Windows Update.
To get the standalone package for this update, go to the Microsoft Update Catalog website.
For a list of the files that are provided in this update, download the file information for cumulative update 4506991.
Information about protection and security
Protect yourself online: Windows Security support
Learn how we guard against cyber threats: Microsoft Security