KB5103214: Microsoft Exchange Server Subscription Security Update (July 2026)

A newer security update for Microsoft Exchange Server 2016 Cumulative Update 23 has shipped since this one: KB5121573 (2026-08-11). For cumulative update families the newer package includes these fixes, so installing that one is usually the shorter path. Verify against your own update rings before you skip this package.

We checked Microsoft's support article for KB5103214 on 2026-08-11 and it lists no known issues. Read the article before broad deployment; Microsoft adds issues as reports come in, and we re-check on every refresh.

KB5103214 is the July 2026 security update delivering Cumulative Update 14 for Exchange Server 2019, so it bundles both feature rollup and security fixes into one on-premises mailbox server package. The per-update CVE detail is still provisional because Microsoft has not published it for this cycle, and the release document maps no named zero-days here, but this remains an internet-facing mail server that attackers target routinely. As a CU rather than a standalone patch, applying it also advances your build baseline, which affects future update eligibility.

Do this: Stage KB5103214 on a non-production Exchange 2019 server first to validate the CU14 upgrade, since cumulative updates change the build and can affect coexistence and transport services.

AI-generated from public data, 2026-07-21. Verify against the vendor advisory before acting.