News

Microsoft Ending Support for .NET Framework 4.5.2, 4.6 and 4.6.1

• By Kurt Mackie
• 04/27/2021

Microsoft this week gave users of older .NET Framework versions about a year's advance notice that product support is running out.

April 26, 2022 will be the date when support ends for .NET Framework versions 4.5.2, 4.6 and 4.6.1. Organizations are advised to upgrade to .NET Framework 4.6.2, at minimum, before that date to stay supported and continue to get security patches.

The most recent version is .NET Framework 4.8, which was released in April 2019. Organizations that get automatic updates through the Windows Update service may already be using this version.

By May 2022, systems not upgraded from .NET Framework versions 4.5.2, 4.6 and 4.6.1 "may be insecure," Microsoft's notice advised. If problems need to be resolved, Microsoft's technical support will request that an upgrade be installed first before proceeding.

Microsoft didn't explain the second deadline of May 2022. Possibly, it's a reference to the arrival of the .NET Framework monthly roll-up, a cumulative update that's scheduled to arrive on May 11 ("update Tuesday"). Microsoft established .NET Framework cumulative updates about five years ago. They arrive on update Tuesdays (the second Tuesday of each month) "via Windows Update, Windows Server Update Services or Microsoft Update Catalog," according to this old Microsoft blog post description.

Microsoft is ending these versions of .NET Framework because they use the insecure encryption protocol Secure Hash Algorithm 1 (SHA-1). SHA-1 is a decades-old security protocol that has been broken by security researchers using fast computers and brute force methods.

Microsoft sees the ending of support for .NET Framework versions 4.5.2, 4.6 and 4.6.1 as not being very disruptive. Only 2 percent of its customers are thought to be using them.

App Compatibility
Microsoft is claiming that in-place upgrades of these older .NET Framework versions to .NET Framework 4.6.2 and newer won't require organizations to recompile their applications. However, organizations should still test their apps before an upgrade.

Here's how the announcement phrased it:

There is no need for you to retarget or recompile against .NET Framework 4.6.2. That said, we strongly recommend you validate that the functionality of your app is unaffected when running on the newer runtime version before you deploy the updated runtime in your production environment.

Organizations experiencing problems with app compatibility, though, can get help from Microsoft's App Assure app compatibility assurance program. It's free for organizations having 150 licenses or more under Microsoft 365 or Windows 10 plans.

If applications aren't compatible with a newer .NET Framework version, then they need to be "migrated," which means that code changes need to be performed in Visual Studio. That detail is mentioned in this document.

More information about the end of .NET Framework 4.5.2, 4.6 and 4.6.1 can be found in this Microsoft FAQ document. It noted that the end of support announcement doesn't apply to the .NET Core and .NET 5 product lifecycles, which remain unchanged.

.NET Framework Support
At their end date, .NET Framework versions 4.5.2, 4.6 and 4.6.1 will have been supported for about seven years each, instead of the expected 10 years, according to release dates shown in this Microsoft document.

.NET Framework is described by Microsoft as being a component in the "Fixed Lifecycle Policy" for its software products. The component's lifespan is tied to the overall Windows platform's lifecycle. Typically that lifespan would be 10 years, but not in this case, so .NET Framework versions 4.5.2, 4.6 and 4.6.1 are getting an early retirement.

Microsoft has carved out a special exception for .NET Framework 3.5 Service Pack 1, which was first released in 2007. It's considered to be a "standalone product" (not a component) with five years of "mainstream" support and five years of "extended" support that's tied to the operating system's lifecycle. .NET Framework 3.5 Service Pack 1 is supported until 2029 on supported Windows systems.