Microsoft Exchange Server Flaw Exploited as a Zero-Day Bug

**CVE-2024-21410** is a critical Exchange Server elevation-of-privilege vulnerability that allows remote, unauthenticated attackers to leak NTLM hashes and perform pass-the-hash/NTLM relay attacks; Microsoft has observed active exploitation (zero-day). Microsoft’s Feb 13 CU14 (2024 H1 cumulative update) enables Extended Protection for Authentication by default to mitigate the issue, and administrators must test EPA and account for compatibility constraints before deploying the update.