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As you already know, we have to patch our Exchange Servers quickly to save our servers from HAFNIUM attack.

Steps :

  • Download Hostfix for Exchange 2013 CU 23 here, If you have older version of CU, you need to first upgrade to Exchange 2013 CU23 and then install KB5000871 hotfix.
  • Before you install this hotfix, keep in mind that services will become in disabled state during installation and it could take few minutes to hours, Hence make sure you take sufficient outage.
  • I have not outlined the way to put your server into maintenance, please follow the process, you used to follow for regular patching of exchange servers.
  • Your owa customizations will be lost, so make sure you take backup etc.


  • Make sure you launch command prompt as “run as administrator”, otherwise you can face issue with the installation.

  • Hotfix makes changes all Microsoft Exchange Services in “disabled” state.
  • You will see multiple files being updated.
  • Gradually, Services will be set to “automatic” and start. Wait sometime for all services to start.
  • FYI, If you had some services in disabled state, those will be respected and kept in disabled state.
  • It took around 30 minute to finish.
  • Take a reboot.
  • Perform Health check of services and then you can include the server back to the traffic.
  • Read more about this update here :

Thanks for reading !