CVE-2026-21265
Secure Boot Certificate Expiration Causes Trust Chain Disruption
Publication date: 2026-01-13
Last updated on: 2026-01-13
Assigner: Microsoft Corporation
Description
Description
CVSS Scores
EPSS Scores
| Probability: | |
| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| microsoft | windows | * |
| microsoft | windows_boot_manager | * |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-1329 | The product contains a component that cannot be updated or patched in order to remove vulnerabilities or significant bugs. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability involves Windows Secure Boot certificates stored in the UEFI KEK and DB that are approaching expiration in 2026. These certificates are critical for maintaining the Secure Boot trust chain, which ensures that only trusted software is loaded during the boot process. If these certificates expire without being updated, Secure Boot functionality can be compromised, potentially allowing security feature bypasses. Additionally, the update mechanism relies on firmware components that may have defects, causing certificate trust updates to fail or behave unpredictably, which can disrupt the Secure Boot trust chain and reduce system security. [1]
How can this vulnerability impact me? :
If the expiring certificates are not updated properly, Secure Boot may fail to function correctly, leading to a loss of security protections during system startup. This can result in the inability to prevent unauthorized or malicious software from loading early in the boot process, increasing the risk of system compromise. Furthermore, defects in firmware components involved in the certificate update process can cause update failures or unpredictable behavior, potentially disrupting the Secure Boot trust chain and exposing the system to security risks. [1]
How can this vulnerability be detected on my network or system? Can you suggest some commands?
This vulnerability relates to expiring Microsoft certificates in the UEFI KEK and DB used by Windows Secure Boot. Detection involves checking the versions and expiration dates of these certificates on affected devices. While specific commands are not provided, administrators should verify the presence and expiration status of the following certificates: Microsoft Corporation KEK CA 2011, Microsoft Corporation UEFI CA 2011, and Microsoft Windows Production PCA 2011. This can typically be done by inspecting UEFI firmware settings or using Windows tools that report Secure Boot certificate information. Due to the nature of the vulnerability, monitoring firmware and OS logs for certificate update failures or Secure Boot trust chain disruptions may also help detect issues. [1]
What immediate steps should I take to mitigate this vulnerability?
Immediate mitigation steps include updating the expiring Microsoft certificates stored in the UEFI KEK and DB to their latest versions to maintain Secure Boot functionality. Because the certificate update mechanism depends on firmware components that may have defects, it is important to carefully validate and deploy these updates to avoid failures or unpredictable behavior. Ensuring devices receive the official Microsoft updates for Secure Boot certificates and verifying successful installation will help prevent security degradation and maintain the integrity of the Secure Boot trust chain. [1]