CVE-2026-62911 Explained: Detecting and Patching the Exchange Auth Bypass
If you manage on-prem Microsoft Exchange, this one's worth five minutes of your time. On August 11, 2026, Microsoft disclosed CVE-2026-62911 — a critical authentication bypass vulnerability (CVSS 8.0) affecting Exchange Server 2016, 2019, and Subscription Edition. The root cause sits in Exchange's MRSProxy endpoint, which fails to enforce Extended Protection for Authentication. That gap lets an attacker relay NTLM credentials from the Exchange machine account and bypass authentication entirely —
🎯 Vulnerability: Remote Code Execution (RCE)
💡 Defense Fix: Avoid executing shell commands via system(). Use parameterized APIs and strict input sanitization.