MC1427604 — Enforcement phase for Kerberos RC4 protections begins with the July 2026 Windows security update

What and whyWindows updates released in July 2026 introduce the enforcement phase of protections designed to address a Kerberos information disclosure vulnerability (CVE‑2026‑20833). This phase completes the transition away from RC4-based Kerberos tickets by removing Audit mode and leaving Enforcement mode as the only supported behavior for Kerberos RC4 usage on Windows domain controllers. With the July 2026 security update installed, domain controllers enforce updated behavior for service accou...

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