CISA Issues Alert on Exploited Microsoft Defender Zero-Day Vulnerabilities

**Executive summary:** CISA warns of two Microsoft Defender zero-day vulnerabilities—CVE-2026-45498 (denial-of-service) and CVE-2026-41091 (link-following privilege escalation)—that have been added to the KEV and are confirmed to be actively exploited; organizations should apply Microsoft patches or mitigations immediately and follow BOD 22-01 guidance. The DoS can disable endpoint protection, the link-following bug can enable local privilege escalation, and combined exploitation could permit full compromise of affected systems.