Mitigating Secure Boot Risks in 2026: A Comprehensive Guide

In June 2026 Secure boot certs start to going to expire for physical en virtual machines Servers en Clients. PS not only Windows but also Linux!!

PS. Make sure Client en Servers all installed with latest updates!!

Made a little Risk Assessment:

The expiration and replacement of Microsoft Secure Boot certificates pose a high risk to IT environments. If not properly managed, systems may fail to boot, updates may fail, and security risks may increase. This is particularly critical in automated and virtualized environments.

Key risks:

 Systems failing to boot after updates
 Incompatibility during OS or hypervisor upgrades
 Increased security risks due to outdated certificates

Recommended actions:

1.Update firmware and Secure Boot certificates
2.Test all workloads in a lab environment
3.Update golden images and automation pipelines

A phased rollout and proper validation are essential to prevent disruptions.

1. Scope

This document describes the risks, impact, and mitigations related to the expiration of Microsoft Secure Boot certificates in enterprise environments.

2. Affected Components

 Systems with UEFI firmware (Servers, Desktops, Virtual Machines)
 Microsoft UEFI CA certificates
 Operating Systems (Servers, Clients) (Windows, Linux)
 Automation tools like (Packer, MDT, SCCM)

3. Risk Analysis

Key risks:

 Incompatibility during upgrades
 Security vulnerabilities caused by outdated trust stores
 Errors in automation pipelines
 Firmware incompatibility

4. Risk Matrix

 Upgrade Issues: High
 Security Exposure: High
 Automation Failures: Medium
 Firmware Issues: High

5. Mitigations

 Update firmware on all systems
 Apply Microsoft Secure Boot updates
 Verify Event ID 1808
 Rebuild images with updated certificates
 Perform a phased rollout

6. Validation & Testing

 Test OS boot scenarios
 Validate Secure Boot status
 Verify automation pipelines

7. Conclusion

Changes to Secure Boot certificates must be treated as critical infrastructure updates. Proper preparation, testing, and phased implementation are essential to avoid disruptions.

.Microsoft has released patch’s for the following OS.

Windows 11 (23H2/24H2/25H2)
Windows Server 2016/2019/2022/2025.

VMware is creating a “Fix or Update” for this

* I did not test versions with extended support like Windows 2012 R2 and Windows 10.

Get your list with:
Get-VM | Where-Object { $_.ExtensionData.Config.Firmware -eq “efi” -and

$_.ExtensionData.Config.BootOptions.EfiSecureBootEnabled } | Select-Object Name,

   @{N=”OS”;E={$_.ExtensionData.Guest.GuestFullName}},  PowerState

There is a updated coming from VMware by Broadcom: Check this article:     @{N=”OS”;E={$_.ExtensionData.Guest.GuestFullName}},  PowerState

https://knowledge.broadcom.com/external/article/423893

Extra Info

Microsoft Info:

I hope that most People have Read: Windows Secure Boot certificate expiration and CA updates

and Secure Boot playbook for certificates expiring in 2026

Redhat:
Secure Boot Certificate Changes in 2026: Guidance for RHEL Environments

Broadcom:
Secure Boot Certificate Expirations and Update Failures in VMware Virtual Machines

Manual Update of the Secure Boot Platform Key in Virtual Machines





Simplified Fix Secure Boot Script for Easy VM Updates

I recently created 3 version of a FixSecureBoot script — a lightweight alternative inspired by the excellent work of haz-ard-9, the author of FixSecureBootBulk.ps1. Their script is powerful and absolutely the right choice if you rely on BitLocker or need a fully automated, safety‑first workflow.

However, at roughly 3,000 lines of code, the original script is understandably complex. It includes many checks and safeguards, which are great for production environments but made it harder for me to fully understand what was happening under the hood. I wanted something simpler, easier to read, and tailored to my own workflow.

So I took the time to study the original script, copied only the parts I needed, and built a much more compact version that gives me exactly the result I want — which show the verification step that every thing is correct updated.

What My Script Does

Here’s the full sequence of actions my simplified script performs:

1.Shuts down the VM
2.Creates a snapshot
3.Enables UEFI Setup Mode
4.Clears VMRAM (for older VMs)
5.Upgrades virtual hardware if the VM is below version 21 (vSphere 8)
6.Starts the VM and waits for VMware Tools
7.Checks that the guest OS is fully online
8.Downloads the required certificates (only once)
9.Uploads the two certificates to the VM if not exist
10.Installs the new boot certificates
11.Shuts down the VM and clears Setup Mode
12.Boots the VM and sets AvailableUpdates to 0x5944 (certs ready for install)
13.Reboots until AvailableUpdates becomes 0x4100 (may require multiple reboots)
14.Reboots and runs Secure-Boot-Update again
15.Reboots and runs Secure-Boot-Update again, then checks for Event ID 1808 (if found, everything is good)

I’ve tested this workflow successfully on:

 Windows 11 (23H2, 24H2, 25H2)
 Windows Server 2016, 2019, 2022, and 2025

Downloads
** link the links for downloading the original files from Microsoft Github page.

WindowsOEMDevicesPK.der
microsoft corporation kek 2k ca 2023.der

Rename microsoft corporation kek 2k ca 2023.der to kek2023.der

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Current Limitation: Packer Integration

CLEAN PACKER BUILD IS NOT SAFE!! AFTER THE BUILD YOU NEED TO RUN FIX SECURE BOOT!!

I don’t yet have a complete fix for integrating this into a full Packer build. For now, I simply pre‑stage the certificates:

Build file:

provisioner “file” {

source = “./setup/SecurebootCert/”

destination = “C:/Windows/Temp”

}

I have build three versions:

Fix_Secure_Boot_Manual.ps1
Fix_Secure_Boot_Single.ps1
Fix_Secure_Boot_Multi.ps1

If you want a script that’s easier to read, easier to modify, and still gets the job done (as long as you’re not using BitLocker), this simplified version might be exactly what you need.

Let me know if you want me to share the script itself or write a follow‑up post about how it works internally.
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Template Check if al ready Updated

If VM check if al ready updated

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Run Script full from Template
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