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KB5103213: what it fixes and who gets it

KB5103213 is a security update from Microsoft's July 2026 release for Microsoft Exchange Server 2019 Cumulative Update 15.

Microsoft data read
4CVEs fixed
1rated Critical
0already exploited
Yesrestart required

Should you install it?

Yes. It closes holes Microsoft rates Critical, the most serious rating it uses. Windows Update installs it automatically on supported home PCs.

If the installation fails or the PC misbehaves afterwards, note the exact error code first: the fix depends on it. Our update troubleshooting guides are linked on this page.

Security fixes in KB5103213

CVETypeCVSSSeverity
CVE-2026-55008Microsoft Exchange Server Spoofing VulnerabilitySpoofing9.6Critical
CVE-2026-55005Microsoft Exchange Server Remote Code Execution VulnerabilityRemote Code Execution8.8Important
CVE-2026-55006Microsoft Exchange Server Elevation of Privilege VulnerabilityElevation of Privilege7.8Important
CVE-2026-55009Microsoft Exchange Server Elevation of Privilege VulnerabilityElevation of Privilege7.8Important

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