We are getting questions from our customers on when they can expect us to release Exchange SE Cumulative Update 1 (CU1). After all, in the past we mentioned that it would be released by the end of the first half of calendar year 2026, later updated to “second half of 2026”. What is the deal? Where is CU1?
Over the last few months, various Microsoft execs made statements explaining how Microsoft is leveraging a variety of AI tools to help find vulnerabilities in our products (examples of such announcements can be found here, here and here).
It should come as no surprise that this is a Microsoft-wide initiative. Many teams, Exchange Server included, are working through reported issues – which includes validation that they are real security issues, reproducing, fixing, testing for regressions / issues after fixes are deployed and releasing updates monthly.
We have been releasing security updates for Exchange Server regularly: May, June, July, August. You can expect this increased pace of security releases to continue. We are prioritizing security above all else.
While all of that is happening, we are also working on CU1; we are regularly rolling our monthly security payload into our internal CU1 build and plan to release Exchange SE CU1 as soon as we get a reasonable stable point and have a month without pressing security payload. We really do not want to try to release a new CU1 and then immediately supersede the new CU with security updates as that would create double the update work for many organization administrators. Even internally, trying to ensure that two major releases (Security Update and a CU) get appropriately tested so we can ensure high quality and nothing falls through the cracks would be very challenging as CU1 must be all inclusive of everything that we released since the RTM.
In short: Exchange SE CU1 is coming; we do not have a date to give you. But we did not forget about it.
Until then, please keep Upgrading your organization to Exchange Server SE | Microsoft Community Hub and if you are already on Exchange Server SE, stay up to date!
The Exchange Server Team
