Microsoft Confirms October Windows Server Updates Break NetApp SMB Shares, Offers a Workaround

Microsoft has confirmed that its October 2026 Patch Tuesday updates are causing authentication failures when users and applications attempt to access NetApp SMB shares on Windows Server.

The issue affects organizations using Azure NetApp Files and NetApp ONTAP, with Microsoft linking the failures to LDAP authentication security improvements introduced in October 2026.

According to Microsoft’s advisory, the changes can prevent affected systems from accessing network resources.

Windows Server LDAP security changes cause NetApp authentication failures

Microsoft introduced stricter LDAP authentication requirements for Active Directory domain controllers with its October 2026 security updates.

The updated authentication process requires a valid LDAP service ticket that matches a registered Service Principal Name (SPN) on the target domain controller.

Previously, certain configurations could authenticate to LDAP using Kerberos tickets intended for other services. However, the new security requirements no longer allow this behavior.

The change affects Azure NetApp Files and NetApp ONTAP configurations that use an LDAP client session security setting of “none.”

These configurations rely on the previous authentication behavior, causing Active Directory domain controllers to reject authentication attempts with “Invalid credentials” errors.

As a result, affected organizations may experience failures when users or applications attempt to access NetApp SMB shares.

Microsoft provides a temporary workaround while NetApp works on a permanent fix

Microsoft has published a temporary registry-based workaround to help organizations restore access to affected NetApp SMB shares.

However, Microsoft warns that administrators should use the workaround only temporarily because it changes security-related settings.

Organizations should review the security implications before applying the workaround and remove it once a permanent solution becomes available.

NetApp is working on a permanent resolution to address the authentication failures, although neither company has announced a release date.

In other Windows Server news, Microsoft recently fixed an RD Web Access issue ahead of the end of XSLT support. The company also confirmed SQL Server connection failures caused by Windows updates.

Via Neowin