SharePoint security fixes released with January 2021 PU and offered through Microsoft Update

Below are the security fixes for the SharePoint OnPrem versions released this month.

SharePoint 2010 Suite:

  • KB 4493187 – SharePoint Foundation 2010
  • KB 4493178 – Word Automation Services for SharePoint 2010
  • KB 4486736 – Excel Services for SharePoint 2010
  • KB 4493183 – Office Web Apps Server 2010

SharePoint 2013 Suite:

  • KB 4493175 – SharePoint Foundation 2013 (core component)
  • KB 4486683 – Word Automation Services for SharePoint 2013
  • KB 4486724 – Excel Services for SharePoint 2013
  • KB 4493171 – Office Web Apps Server 2013

SharePoint 2016 Suite:

  • KB 4493163 – SharePoint Server 2016 (language independent)
  • KB 4493167 – SharePoint Server 2016 (language dependent)

SharePoint 2019 Suite:

  • KB 4493162 – SharePoint Server 2019 (language independent)
  • KB 4493161 – SharePoint Server 2019 (language dependent)

Office Online Server:

  • KB 4493160 – Office Online Server
See the Security Update Guide below for more details about the relevant fixes:

More information:

Please ensure to have a look at the SharePoint Patching Best Practices before applying new fixes.


  1. Hi Stefan, Happy New Year!
    One question about patching… For fix this issues:

    Fixes an issue in which the navigation pane will be hidden when users change some Search Admin settings in a Search Service Application.
    Fixes an issue in which Business Connectivity Services (BCS) crawls of the .NET Connectivity Assemblies, Web services or Custom type don’t work.

    I noticed in various Microsoft articles that you need to install multiple patches to fix the problem, in particular this:

    Description of the security update for SharePoint Foundation 2013: December 8, 2020 (KB4493138)
    Description of the security update for SharePoint Foundation 2013: December 8, 2020 (KB4486696)
    December 8, 2020, update for SharePoint Enterprise Server 2013 (KB4486758)

    About January PU which patch should i install to reproduce the December patches listed above?

    Thank you very much


  2. I have installed January patches for 2013 and 2016 and I think there is problem with patch at these two version which is the database schema version not updated to January it keeps December version.


  3. Does January CU has a bug fix for September’s SharePoint 2016 release?


    1. For which issue exactly are you looking for a fix?


  4. After installing KB 4493182 – Project Server 2010 January 2021 CU, I am getting below error message.

    Could not found Microsoft.Office.Project.PWa.Applicationpages.ProjectDrillDownPage from assembly ‘Microsoft.Office.project.Server.Pwa.ApplicationPages’


    1. Hi Prasad,
      did you run the SharePoint Configuration Wizard after installing the fix?


    2. Hi Prasad,

      this has been identified as a problem introduced with December 2020 CU.
      A fix is in the works.

      Please apply the following workaround:

      Create a backup of the ProjectDrillDown.aspx page.
      Afterwards change the ProjectDrillDown.aspx to fix the incorrect information within it.

      The pertinent information changes from this:

      <%@ Page Language=”C#” MasterPageFile=”~masterurl/default.master” Inherits=”Microsoft.Office.Project.PWA.ApplicationPages.ProjectDrillDownPage,Microsoft.Office.Project.Server.PWA.ApplicationPages

      to this:

      <%@ Page Language=”C#” MasterPageFile=”~masterurl/default.master” Inherits=”Microsoft.Office.Project.PWA.ProjectDrillDownWebPartPage,Microsoft.Office.Project.Server.PWA



  5. Yes
    It was successfully completed , I cross checked that Central admin > upgrade and Migration> check upgrade status and also update the Patch and Build version as well


    1. After installation of fix – restarted all Servers and run SharePoint Configuration wizard successfully


      1. Hi Stefan, could you please help me on this I was badly stuck, please let me know if you need any further details


        1. Hi Prasad,
          if you need assistance to get this solved, please open a ticket with Microsoft Support.


  6. Hey, Thanks for sharing the news about the patch. This is super helpful and solved many issues for me.


  7. Question on the January patch, specifically KB4493163 and the csisrv.dll file. Our SharePoint servers failed a NESSUS scan showing the csisrv.dll file was dated November 2020 (16.0.5095.1000). I confirmed after installing January 2021 patches and PSCONFIG (no errors, no warnings), this file did not update to what is shown in the January 2021 patch list.. I downloaded the list of files for the patch and it shows it should have been dated December 2020 (16.0.5110.1000). I have three SharePoint 2016 farms and four separate servers and all have the same outdated version of csisrv.dll. Have you seen anything on this or can anyone confirm? In any regards, I will wait until the February 2021 patches are released and see if this updates then. This is considered a CAT I critical finding and raises alarms across our institute.


    1. Hi Debra,
      I would suggest to open a ticket with Microsoft to get this investigated.


  8. Sharepoint 2013. Installed patches and now have HTTP Error 503. The service is unavailable. I ran the configuration wizard (gui) but it failed. Ran the configuration wizard from CL (PSConfig.exe -cmd upgrade -inplace b2b -force -cmd applicationcontent -install -cmd installfeatures) and it fails.

    Event log shows Event ID 2583 The database schema version is less than the minimum backwards compatibility schema version that is supported for this component.


    1. Hi Patrick,
      looking at the symptoms its not clear what went wrong.
      I would recommend to open a support case with Microsoft to get this analyzed.


Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.