DHCP-Bug in Update KB4338814 (Windows 10 Version 1607)

[German]A short note to administrators running Windows Server version 1607 als DHCP failover server. Cumulative update KB4338814 causes a bold DHCP bug during installation, so that Windows 10 Enterprise clients no longer have a network connection.


The problem is actually limited to a small group of users, since Microsoft has discontinued support for the Anniversary Update (V1607) of Windows 10 Home and Pro (see Windows 10: End of Life for several builds). Only Windows 10 Enterprise and Education and Windows Server 2016 (and LTSC versions) still receive this update.

Unofficially, it should also be installable for Home and Pro, since CloverTrail machines receive support until 2023 (see Windows 10 support for Clover Trail machines till 2023). However, these machines are not affected by the bug, as it only affects clients via DHCP failover servers.

Update KB4338814 for Windows 10 Version 1607

For this reason I had only briefly mentioned KB4338814 update in my blog post Patchday: Windows 10-Updates July 10, 2018. Microsoft writes that the update contains quality improvements and addresses the following issues:

  • Updates Internet Explorer's Inspect Element feature to conform to the policy that disables the launch of Developer Tools.
  • Addresses an issue that, in some cases, causes the wrong IME mode to be chosen on an IME-active element.
  • Addresses an issue where DNS requests disregard proxy configurations in Internet Explorer and Microsoft Edge.
  • Addresses additional issues with updated time zone information.
  • Updates support for the draft version of the Token Binding protocol v0.16.
  • Evaluates the Windows ecosystem to help ensure application and device compatibility for all updates to Windows.

And the package contains security updates to Internet Explorer, Microsoft Edge, Windows apps, Windows graphics, Windows datacenter networking, Windows virtualization, Windows kernel, and Windows Server. This update is not available with express installation files for Windows Server 2016.

Microsoft revealed a DHCP issue on Servers

I didn't explicitly address it in the blog post Patchday: Windows 10-Updates July 10, 2018(I'm not sure if it was already included in the KB article). Blog reader Thorsten has touched it in this comment and at reddit.com there is this thread to it. On reddit an administrator is annoyed that the KB4338814 update is pushed to his machines via WSUS, although there is a known issue. Microsoft writes under KB4338814 that there is a known problem with this update.

Ich hatte es im Blog-Beitrag Patchday: Windows 10-Updates 10. Juli 2018 nicht explizit adressiert (bin mir auch nicht sicher, ob es da schon im KB-Artikel enthalten war). German blog reader Thorsten left a comment and also at reddit.com there is this thread pointing out the issue. The reddit user shouts that update KB4338814 is been pushed via WSUS an his machines, althought there is a 'known issue'. Microsoft writes in article KB4338814 about that issue.


After installing this update on a DHCP Failover Server, Enterprise clients may receive an invalid configuration when requesting a new IP address.  This may result in loss of connectivity as systems fail to renew their leases.

Unfortunately, there is no workaround except to block the update. Microsoft is working to fix the bug and hopes that it can be fixed by mid-July 2018. Is anyone affected by this problem?

Addendum 1:  The DHCP bug affects also Windows 10 V1803 with update KB4338819 installed. And a German blog reader has posted a workaround here as a comment – maybe it helps.

Addendum 2: Microsoft has released fixes for Windows 10, see Windows 10: Update revisions July 16, 2018.

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