Exchange Server SE CU1 Delayed Amid Ongoing Security Reviews

Microsoft's Exchange Server SE Cumulative Update 1 (CU1) has been delayed due to ongoing security reviews and patch releases. Engineers are working through AI-assisted security findings, which have surfaced a number of potential issues that require validation and remediation.

The update was initially expected by the end of the first half of 2026, but Microsoft's roadmap now targets the second half of the year. However, no firm release date has been set yet.

Microsoft is using AI tools to help identify vulnerabilities in Exchange Server SE, and engineers must still determine whether each report represents a genuine security problem. This process requires reproducing the issue, developing a fix, and testing for regressions.

In the meantime, Microsoft continues to release regular security updates, which administrators should prioritize over waiting for CU1. The August 2026 Exchange Server Security Updates were released on August 11, and organizations can continue to apply these updates without delay.