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Active Directory Domain Controller security hardening patch breaks legacy LDAP authentication for corporate multi-function printers

Rakesh Sharma 20 Reputation points
2026-06-09T04:35:56.63+00:00

Hi everyone, following the latest security hardening update applied to our Windows Server domain controllers, none of our warehouse multi-function office scanners can scan-to-email anymore. The scanners use LDAP to lookup user addresses. The printer logs show an authentication dropped error because the server now strictly requires LDAP channel binding.

Windows for business | Windows 365 Business
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Harry Phan 22,470 Reputation points Independent Advisor
2026-06-09T06:57:51.16+00:00

Hi Rakesh,

After the latest security update, your scanners stopped working because the domain controllers now require a more secure way of talking to them. The scanners were using an older LDAP method that isn’t allowed anymore, so the server rejects their requests. To fix this, the devices need to support secure LDAP (called LDAPS), usually by updating their firmware or changing their settings to use port 636 with encryption. If the scanners are too old to handle LDAPS, the only option is to loosen the new security rules on the server, but that reduces protection and isn’t recommended. In short, the network is fine, the issue is that the scanners must be updated or reconfigured to use the newer secure method.

You can start by checking scanner LDAPS support and reviewing LDAP channel binding requirements.

Harry.

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