Citrix XenApp 6.5 Hotfix Rollup Pack 3 is available since the 12nd of December 2013 (link) and I went through several deployment until today. I got this error on a worker server (PVS Golden image) while installing this update. The error : "Error 25822. Setup could not install the drivers required for this product." stop the installation process and rollback to the original state of the XenApp server. As the installation wen fine on other servers within the same farm, I chose to take some time to investigate this issue. First thing first, running the patch update by generating a log file with msiexec : and when i opened the log file i found the error : The installer stop because the file ctxsbx.inf is not found on the XenApp server, after a google search i found this old XenApp KB CTX121887. As mention in this kb I made a copy of this file on the target XenApp server from another one where the file is. It did work but after that the installer remaion stuck on drivers installation process and remain on loops. The only way to make sure my server would survibe this installation was to cancel everything, repair the XenApp installation and reboot the server at the end. Once the server was back online again, I tried to apply the HRP3 again and everything went finaly fine.