KB4011021 May Fail to Install for Office Online Server

EDIT: 1/18/2018: This update has been replaced by KB4011022.

KB4011021 may fail to install for Office Online Server. This appears to be due to a failure to install the GAC binaries. To prevent a partial installation of this KB, I would suggest holding off on applying this to production systems. The wacserver-x-none_MSPLOG.LOG installation log file will have entries similar to the below.

01/11/2018 12:33:39.445 [12820]: Assembly Install: Failing with hr=80070005 at RemoveDirectoryAndChildren, line 393
01/11/2018 12:33:39.445 [12820]: Detailed info about C:\Windows\assembly\temp\SP0ZKA0QET\Microsoft.Office.Web.Apps.Environment.WacServer.intl.dll
01/11/2018 12:33:39.445 [12820]: File attributes: 00000080
01/11/2018 12:33:39.476 [12820]: Restart Manager Info: 1 entries
01/11/2018 12:33:39.476 [12820]: App[0]: (10644) Windows PowerShell (), type = 5
01/11/2018 12:33:39.476 [12820]: Security info:
01/11/2018 12:33:39.476 [12820]: Owner: S-1-5-18
01/11/2018 12:33:39.476 [12820]: Group: S-1-5-18
01/11/2018 12:33:39.476 [12820]: DACL information: 5 entries:
01/11/2018 12:33:39.476 [12820]: ACE[0]: Type = 0x00, Flags = 010, Mask = 001f01ff, SID = S-1-5-18
01/11/2018 12:33:39.476 [12820]: ACE[1]: Type = 0x00, Flags = 010, Mask = 001f01ff, SID = S-1-5-32-544
01/11/2018 12:33:39.476 [12820]: ACE[2]: Type = 0x00, Flags = 010, Mask = 001200a9, SID = S-1-5-32-545
01/11/2018 12:33:39.476 [12820]: ACE[3]: Type = 0x00, Flags = 010, Mask = 001200a9, SID = S-1-15-2-1
01/11/2018 12:33:39.476 [12820]: ACE[4]: Type = 0x00, Flags = 010, Mask = 001200a9, SID = S-1-15-2-2

If you have attempted to install and the installation failed, re-install the November 2017 ISO and subsequently install KB4011020.

Trevor Seward is a Microsoft Office Apps and Services MVP who specializes in SharePoint Server administration, hybrid scenarios, and SharePoint Online. He has been working with SharePoint for 16 years from SharePoint 2003 on up, managing environments with terabytes of content for 150,000+ user organizations. Trevor is an author of Deploying SharePoint 2016 and Deploying SharePoint 2019. You can find him on Twitter and in /r/sharepoint.