CVE-2026-21265

CVE-2026-21265 addresses the impending expiration of Microsoft certificates within Windows Secure Boot's UEFI KEK and DB, affecting Microsoft products. Failure to update these certificates before their June/October 2026 expiration dates could disrupt Secure Boot functionality and compromise security. The vulnerability has a CVSS score of 6.4 (Medium), indicating a high-privilege, local attack with high impact on confidentiality, integrity, and availability, complicated by potential firmware defects during updates. While there is no known active exploitation or public exploit code, the vulnerability has garnered significant community discussion and media coverage, highlighting its importance.