LDAP-Bug in Updates KB4034679, KB4034664, KB4034670

Windows Update[German]Updates KB4034664 and KB4034679 (August 8, 2017), and Preview Rollup Update KB4034670 (August 15, 2017) is causing issues with LDAP (Lightweight Directory Access Protocol).


I haven't covered this issue due to the rendering bug (see Windows Update KB4034664 is causing trouble on 2nd screen). But Updates KB4034679, KB4034664 and KB4034670 are causing serious issues with Lightweight Directory Access Protocol (LDAP). Microsoft has added recently a note to its know issues section in all knowledge base articles. They wrote:

Due to a defect in WLDAP32.DLL, applications that perform LDAP referral chasing can consume too many dynamic TCP ports (potentially exhausting them) after installing KB4025337 and KB4025341. Applications and roles known to make these referrals may include Outlook.exe, DFSR, and others.

A broken WLDAP32.DLL is causing this issue during Referral chasing after installing the updates. Microsoft proposes the following workaround:

To work around the problem, restart services or applications that perform LDAP referral chasing to free TCP dynamic ports. A reboot will also free ports. For example, restarting Outlook will free ports used by that application.

Microsoft says, that a restart of application will show also this behavior, if updates KB4025337 and KB4025341 are installed:

If restarting applications that perform LDAP referral chasing returns normal functionality on machines that installed KB4025337 and KB4025341, you may be experiencing this issue.

Microsoft's proposal for a Workaround is:

To work around the problem for cluster computers hosting the DFSR service, place the virtual cluster object under the Computers container to avoid reaching the referral chasing search, which leads to the dynamic port leak.

Microsoft is working on a resolution and (hopefully) will provide an update in an upcoming release.


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