MC1218691 — Initial deployment phase for Kerberos RC4 hardening begins with the January 2026 Windows security update

Windows updates released on and after January 13, 2026, introduce the first phase of protections addressing a Kerberos information disclosure vulnerability (CVE‑2026‑20833). These updates introduce new auditing and optional registry controls that devices can use to begin reducing reliance on RC4 encryption. They also help prepare domain controllers for a future shift to AES‑SHA1 as the default Kerberos encryption method for accounts without explicit encryption settings. The initial deployment ph...

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