Windows Server 2025: Hot Patching Revolution

Game-changing security updates without the downtime

📘 Introduction: The End of Patch Tuesday Reboots

Windows Server 2025 introduces a game-changing feature: Hot patching. This innovation allows you to apply critical security updates without rebooting your servers—dramatically reducing downtime and improving operational continuity.

Hot patching is a transformative update mechanism that allows security patches to be applied to running systems without requiring a reboot. Traditionally, updates—especially those released on Patch Tuesday—necessitate downtime and service disruption. Hot patching eliminates this by modifying in-memory code and updating backing files on disk, ensuring both immediate protection and long-term persistence.

Whether you're managing VMware clusters, deploying hybrid cloud workloads, or automating patching pipelines in DevOps, Hot patching is a must-know capability.

❓ What Is Windows Server Hot Patching?

Hot patching is a method of applying security updates directly to the in-memory code of running processes—without restarting the OS or the application. This means:

• ✅ No reboots for most monthly updates

• ⚡ Faster patch deployment

• 🔄 Reduced workload disruption

• 📈 Improved uptime for mission-critical systems

Additional Benefits:

• 📉 Fewer binaries mean updates install faster and consume less disk and CPU resources

• 🔐 Better protection, as Hotpatch update packages are scoped to Windows security updates that install faster without requiring a reboot

• 🛡️ Reduces exposure time to security risks and simplifies patch orchestration with Azure Update Manager

🏗️ Architecture Overview

🔄 In-Memory Code Modification

Hot patching works by directly updating the code of running processes in RAM. This avoids restarting services or rebooting the server, preserving uptime and user productivity.

💾 Backing Files Update

To ensure persistence, the patch mechanism also updates the corresponding files on disk (e.g., DLLs in C:\Windows\System32). This guarantees that the patched code remains active even after a reboot.

📊 Baseline + Delta Model

1. Baseline: Every quarter (January, April, July, October), a cumulative update is applied with a reboot

2. Hotpatches: For the next two months, Microsoft releases in-memory patches that don't require reboots

Planned Reboots: 12 per year → 4 per year (67% reduction)

This dramatic reduction is ideal for high-availability clusters, production workloads, and DevOps CI/CD pipelines.

Pit-Stop Analogy: Think of Hotpatching as swapping tires while the race-car (your server) is still on the track—no need to pull into the garage for a full overhaul.

🧰 Deployment Checklist

🖥️ Supported Platforms

Azure & Azure Local VMs

Hotpatching is supported on specific combinations of publisher, OS offer, and SKU:

2025-Datacenter-Azure-Edition
2025-Datacenter-Azure-Edition-Core |

Note: Windows Server container base images, custom images, or any other combinations are not supported.

Azure Arc-Connected Machines

• Available for Windows Server 2025 Datacenter Edition and Standard Edition

• Requires enabling the feature in the Azure Arc Portal

• Available for a monthly subscription fee

🔄 Patch Orchestration Process

Azure

• Automatic VM Guest Patching is enabled by default

• Hotpatches are applied during off-peak hours in the VM's time zone

• Azure uses platform health signals to monitor patch success

• Manual patching available via Azure portal or PowerShell (Get-HotFix)

Azure Local & Azure Arc

Patch orchestration options include:

• Azure Update Manager (Arc only)

• Group Policy

• SCONFIG (for Server Core)

• Third-party tools

⚠️ Important Limitations & Considerations

Rollback Reality Check: Unlike traditional updates, hotpatch updates do not support automatic rollback. If issues occur, you must uninstall the latest update and reinstall the last functional baseline—this process requires a reboot.

Coverage Limitations:

• Hotpatching does not cover non-security updates, .NET updates, or driver/firmware patches

• Requires careful planning around baseline cycles and emergency updates

• Container environments have limited support and require separate strategies

🚀 Getting Started

Ready to revolutionize your patch management strategy? Start by evaluating your current Windows Server infrastructure and identifying candidates for Windows Server 2025 migration. Focus on high-availability workloads where downtime reduction will have the greatest impact.

For detailed implementation guidance and best practices, consult us.