Windows - Configuration - Install Out-Of-Band Patch (MSU)

What the Out-Of-Band Patch Installer does

This Automox Worklet™ automates the deployment of out-of-band Microsoft patches to Windows endpoints by downloading MSU (Microsoft Update Standalone) files directly from the Microsoft Update Catalog and installing them via the WUSA.exe tool. Out-of-band patches are critical security updates released outside the standard monthly update cycle, often addressing zero-day vulnerabilities or urgent system issues.

The Worklet checks whether the target KB article is already installed before attempting remediation. If the patch is missing, it downloads the MSU file to a temporary staging directory, executes a silent installation without requiring a restart, and then verifies successful installation by checking the system hotfix registry.

This approach supports both workstations and servers running any supported Windows version. The Worklet handles only MSU-formatted patches; CAB and EXE-based updates require different deployment methods.

Why deploy patches through Automox

Out-of-band patches address critical vulnerabilities that cannot wait for the standard monthly patch cycle. By automating their deployment through Automox, you reduce the time window during which endpoints remain vulnerable to known exploits, such as zero-day attacks or actively exploited vulnerabilities.

Manual patch installation across dozens or hundreds of endpoints introduces inconsistency and human error. This Worklet eliminates variability by enforcing consistent deployment across your entire fleet and providing clear status reporting through the Automox console. You also avoid the overhead of coordinating change windows or scheduling maintenance with end users.

For IT operations teams managing security compliance frameworks such as CIS Benchmarks or NIST 800-53, this Worklet helps demonstrate consistent patch management practices and rapid vulnerability remediation to auditors and stakeholders.

How out-of-band patch installation works

1. Evaluation phase: The Worklet checks the target endpoint for the specified KB article using PowerShell's Get-HotFix cmdlet. If the hotfix is already installed, the Worklet exits with a success status to avoid redundant operations. If the hotfix is missing, the Worklet proceeds to remediation.

2. Remediation phase: The Worklet creates a temporary staging directory at C:\Temp\UpdateStaging\, enables TLS 1.2 for secure downloads, downloads the MSU file from the Microsoft Update Catalog URL, executes WUSA.exe with the /quiet and /norestart flags for silent installation, verifies the hotfix installation by checking Get-HotFix again, and then cleans up temporary files. If installation fails or the hotfix is not applicable to the endpoint, the Worklet reports the failure.

Out-of-band patch installation requirements

• Windows endpoints with any supported operating system version (Windows 10, Windows 11, Windows Server 2016 and later)

• Administrative privileges required for WUSA.exe execution and hotfix installation

• Internet connectivity to download MSU files from Microsoft Update Catalog or an internal repository

• PowerShell available on the endpoint (standard on all Windows systems)

• MSU-formatted patch files only; CAB or EXE patches require alternative deployment methods

• Sufficient disk space in C:\Temp\ for temporary staging during download and installation

• TLS 1.2 support enabled in the .NET ServicePointManager for secure HTTPS downloads

Expected system state after patch installation

After successful remediation, the target KB article is registered in the Windows hotfix database and confirmed via Get-HotFix query. The endpoint reflects the patch in Windows Update history, system properties, and local security event logs. Depending on the KB article, the patch may require a restart to fully activate; the Worklet defaults to silent installation without restart, but you can enable the Worklet's native restart feature if your organization requires immediate activation.

Failed installations are clearly reported with error details, allowing you to investigate specific endpoints that rejected the patch due to hardware incompatibility, dependency issues, or application conflicts. This visibility ensures you address problem endpoints and maintain accurate compliance records for security audits.

How to validate install out-of-band patch (msu) changes

1. Run this Worklet on a pilot Windows endpoint and review evaluation output for install out-of-band patch (msu).

2. Confirm Automox activity logs show successful completion and exit code 0.

3. Verify endpoint state using checks aligned to evaluation script logic, such as Get-HotFix, Write-Output.

4. Validate remediation effects from script operations such as New-Item, Out-Null, Write-Output, then rerun evaluation for compliance.