CISA Warns of Microsoft Exchange and Windows CLFS Vulnerabilities Exploited in Attacks

CISA issued an urgent advisory warning that threat actors are actively exploiting two severe Microsoft flaws — CVE-2023-21529 (Exchange Server RCE via deserialization) and CVE-2023-36424 (Windows CLFS local out-of-bounds read enabling privilege escalation). Both vulnerabilities were added to CISA’s Known Exploited Vulnerabilities catalog; federal agencies must apply available patches by April 27, 2026, and private organizations are strongly urged to prioritize remediation and monitor affected Exchange and Windows environments for suspicious activity.