Hotpatching: What It Is and Why It Matters

Hotpatching allows for the installation of security-relevant updates without requiring a system restart. This is achieved by patching the running code directly in working memory.

The service, currently in free preview, will transition to a paid subscription model costing $1.50 per CPU core per month. (1)

The key innovation is that systems outside of Azure, such as those in on-premises or multi-cloud scenarios, can now utilize hotpatching if integrated via Azure ARC. This integration is a prerequisite for the service.

The Catch: Mandatory Baseline Updates

Despite the benefits of hotpatching, complete restarts aren’t entirely eliminated. Microsoft plans four annual “Baseline” updates in January, april, July, and October. During these months, administrators must schedule a full reboot.

Despite hot patching, a complete restart is not completely saved: Microsoft continues to plan four so-called “Baseline” updates per year, each in January, April, July and October.

For the remaining eight months, security updates can be applied via hotpatch, reducing planned downtime and mitigating risks associated wiht delayed patches.

Microsoft cites its own experience with the Xbox team, where hotpatching shortened work processes from weeks to days.A total of eight hot patches are planned annually, alongside the four mandatory Baseline updates.

In remarkable cases, such as severe vulnerabilities, Microsoft may release a complete update during a “hot patch month” that necessitates a restart.

Azure Exception and Subscription Details

Customers running Windows Servers in Azure environments can continue using hotpatching for free, provided they use Azure Editions of Windows Server 2022 or 2025. In these instances, an additional ARC connection is not required.

administrators in the preview program should note that unless they actively opt out by June 30, they will automatically transition to the paid subscription.

Requirements and Activation Process

Hotpatching requires Windows Server 2025 Standard or Datacenter editions. Servers must be integrated via Azure ARC, with administration handled through the Azure Portal in the “Update Manager” area.

While the ARC connection is free, accessing other Azure services like Microsoft Defender for Cloud or Azure Monitor requires separate licenses.

FAQ: Windows Server Hotpatching

• What is Windows Server Hotpatching?

  It’s a feature that allows security updates to be installed without requiring a server restart.

• When does the paid subscription start?

  July 1, 2025.

• How much does it cost?

  $1.50 per CPU core per month.

• Is Azure ARC required?

  Yes, for on-premises and multi-cloud environments, but not for Azure Editions of Windows Server.

• Are restarts completely eliminated?

  No,four “Baseline” updates per year still require a full reboot.