Exchange 2016 CU22 Upgrade fails

calendar Mar 3, 2025 · 1 min read · microsoft  ·
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An unexpected error when upgrading Exchange.

Symptoms

When patching Exchange 2016 up to CU22 the maintenance step is successful, using the script from a mounted ISO.

1E:\scripts\StartDagServerMaintenance.ps1 -servername myExchangeServer

Setup starts as expected from the command line but then stops almost immediately, just after the Copying Files command.

1e:\setup.exe /m:upgrade /IAcceptExchangeServerLicenseTerms_DiagnosticDataON #CU22

The Exchange setup log shows the following two lines:

1The registry key, HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Exchange\v8.0, wasn't found.
2The registry key, HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\ExchangeServer\v14, wasn't found.

When running the GUI version of Setup, it progresses as far as getting a file copy error.

Cause

Upon further investigation the downloaded ISO was around 2GB in size rather than 6GB. Somehow the download/copy had corrupted or stopped partway through but left enough of the ISO for it to mount correctly and setup.exe and the maintenance mode script to run.

Solution

Re-download the CU22 ISO and reattempt the upgrade.