CVE-2026-21265
MediumCVSS 6.4Exploitation Probability (EPSS)
Elevated risk58th percentile - higher than 58% of all known CVEs
Summary
The vulnerability involves expiring Microsoft certificates in Secure Boot. Failure to update them may cause loss of Secure Boot functionality and protection against malware. The update process can be disrupted by firmware defects.
Risk Assessment
The organization may lose trust in the Secure Boot chain, allowing unauthorized software to run during boot and compromising system integrity.
Recommendation
Immediately update Secure Boot certificates per Microsoft guidelines and verify the update on all devices.
Original NVD description (English source)
Windows Secure Boot stores Microsoft certificates in the UEFI KEK and DB. These original certificates are approaching expiration, and devices containing affected certificate versions must update them to maintain Secure Boot functionality and avoid compromising security by losing security fixes related to Windows boot manager or Secure Boot. The operating system’s certificate update protection mechanism relies on firmware components that might contain defects, which can cause certificate trust updates to fail or behave unpredictably. This leads to potential disruption of the Secure Boot trust chain and requires careful validation and deployment to restore intended security guarantees. Certificate Authority (CA) Location Purpose Expiration Date Microsoft Corporation KEK CA 2011 KEK Signs updates to the DB and DBX 06/24/2026 Microsoft Corporation UEFI CA 2011 DB Signs 3rd party boot loaders, Option ROMs, etc. 06/27/2026 Microsoft Windows Production PCA 2011 DB Signs the Windows Boot Manager 10/19/2026 For more information see this CVE and Windows Secure Boot certificate expiration and CA updates.