Microsoft has released Security Updates (SUs) for vulnerabilities found in:
Exchange Server Subscription Edition (SE)
Exchange Server 2019
Exchange Server 2016
SUs are available for the f...
Updated Feb 13, 2026
Version 3.0
Blog Post
Hello,
Installation of Feb26SU on my first node failed with error 1603. I stopped here and did not try installing it on another node.
Here is the error seen on the installation log file:
Property(C): INTERIMUPDATEINSTALLEDPROPERTY = 5074992
Property(C): KB5066373 = KB5066373
Property(C): msgINTERIMUPDATEDETECTED = Unable to install because a previous Interim Update for Microsoft Exchange Server Subscription Edition has been installed. Please use Add/Remove Programs to uninstall the Interim Update before running this setup again.
Property(C): msgRequiresProc = The version of this file is not compatible with the version of Microsoft Exchange Server Subscription Edition that you're running. Check your computer to see whether you need an x64 (64-bit) or x86 (32-bit) version of this file.
[...]
Property(C): msgInterimIncorrectRollup = Installation cannot continue. The Setup Wizard has determined that this Interim Update is incompatible with the current Microsoft Exchange Server Subscription Edition configuration.
I also ended up with disabled services as per SteveCox post (thanks!) with some extra ones:
BITS
FMS
RemoteRegistry
SearchExchangeTracing
Winmgmt
I am running Exchange Server SE RTM Dec25SU (build 15.2.2562.35) and I used the ExchangeSubscriptionEdition-KB5074992-x64-fr.exe update file (correct checksum).
Any idea?