Revised 6/8/2021: On June 8th, 2021, this update was released to replace a previous update to address a “revocation server was offline” error that may occur during installation. If you’ve already installed a previous release of this update, no action is required.

Revised 4/15/2021: On April 13th, 2021, this update was released to replace a previous release of this some updates. See known issues section for more details. If you’ve already installed a previous release of an affected update, no action is required.

Today, we are releasing the May 2020 Security and Quality Rollup Updates for .NET Framework.

Security

CVE-2020-0605 – .NET Framework Remote Code Execution Vulnerability

A remote code execution vulnerability exists in .NET software when the software fails to check the source markup of a file. An attacker who successfully exploited the vulnerability could run arbitrary code in the context of the current user. If the current user is logged on with administrative user rights, an attacker could take control of the affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.

Exploitation of the vulnerability requires that a user open a specially crafted file with an affected version of .NET Framework. In an email attack scenario, an attacker could exploit the vulnerability by sending the specially crafted file to the user and convincing the user to open the file.

The security update addresses the vulnerability by correcting how .NET Framework checks the source markup of a file.

CVE-2020-1108 – .NET Framework Denial of Service Vulnerability

A denial of service vulnerability exists when .NET Core improperly handles web requests. An attacker who successfully exploited this vulnerability could cause a denial of service against a .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 .NET Core application.

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

CVE-2020-1066 – .NET Framework Elevation of Privilege Vulnerability

An elevation of privilege vulnerability exists in .NET Framework which could allow an attacker to elevate their privilege level.

To exploit the vulnerability, an attacker would first have to access the local machine, and then run a malicious program.

The update addresses the vulnerability by correcting how .NET Framework activates COM objects.

Quality and Reliability

This release contains new quality and reliability improvements for Server 2008 SP1, Windows 7 SP1, Windows Server 2008 R2 SP1, and Windows 10 1703 (Creators Update) that were previously released for other versions of Windows in the February 2020 Preview of Quality Rollup.

Known issues in this security update

Getting the Update

The Security and Quality Rollup is available via Windows Update, Windows Server Update Services, and Microsoft Update Catalog. The Security Only Update is available via Windows Server Update Services and Microsoft Update Catalog.

Microsoft Update Catalog

You can get the update via the Microsoft Update Catalog. For Windows 10, NET Framework 4.8 updates are available via Windows Update, Windows Server Update Services, Microsoft Update Catalog. Updates for other versions of .NET Framework are part of the Windows 10 Monthly Cumulative Update.

**Note**: Customers that rely on Windows Update and Windows Server Update Services will automatically receive the .NET Framework version-specific updates. Advanced system administrators can also take use of the below direct Microsoft Update Catalog download links to .NET Framework-specific updates. Before applying these updates, please ensure that you carefully review the .NET Framework version applicability, to ensure that you only install updates on systems where they apply.

The following table is for Windows 10 and Windows Server 2016+ versions.

The following table is for earlier Windows and Windows Server versions.

Previous Monthly Rollups

The last few .NET Framework Monthly updates are listed below for your convenience:

* March 2020 Update for Windows 10 1607 (Anniversary Update) and Windows Server 2016 * February 2020 Preview of Quality Rollup for Windows 10 1909, Windows 10 1903, Windows Server, version 1909 and Windows Server, version 1903 * February 2020 Preview of Quality Rollup * February 2020 Security and Quality Rollup