The problem is the fallback . If the DC can't find the strong binding (perhaps due to an old certificate or a misconfigured attribute), it happily accepts the weak mapping. Attackers specifically craft their exploits to trigger that fallback path, bypassing strong binding entirely.
For years, most admins ignored it. But in 2024/2025, ignoring this setting is a security risk you cannot afford to take.
Hardening Windows Authentication: A Deep Dive into StrongCertificateBindingEnforcement strongcertificatebindingenforcement
An attacker with a valid certificate (even one belonging to a different user) could alter the Subject or SAN before sending it to the DC. If the weak mapping didn't enforce a cryptographic check, the DC might accept the forged identity.
This led to the infamous scenario, where an attacker could impersonate a privileged user simply by presenting a certificate with a spoofed SAN. The Fix: Strong Certificate Binding Enter Strong Certificate Binding . The problem is the fallback
Instead of just looking at the human-readable fields in the certificate, the DC now verifies a cryptographic link between the certificate and the user object in Active Directory. It checks the (or the entire certificate) against a value stored in the user’s msDS-KeyCredentialLink attribute.
Here is your 3-step migration plan:
If the crypto doesn’t match the claimed identity, authentication fails. Microsoft introduced the StrongCertificateBindingEnforcement registry key (located under HKLM\SYSTEM\CurrentControlSet\Services\Kdc ) to control this behavior. It accepts three values: