Microsoft · Security update · June 9, 2026

KB5103215: June 2026 security update

KB5103215, released June 9, 2026, fixes 11 CVEs in Microsoft Exchange Server 2016 Cumulative Update 23. None of them is reported as exploited. Patch Radar priority: Urgent.

Urgent
CVEs closed
11
1 rated Critical
Exploited
0
None reported
Exploitation more likely
1
Vendor assessment
Highest EPSS
0.1964
97th percentile

Priority of the 11 CVEs

Patch now 0 Urgent 1 High 7 Routine 3

Applies to

Product
Microsoft Exchange Server 2016 Cumulative Update 23

CVEs this fix closes

PriorityCVEComponentImpactCVSSEPSSExploitation
Urgent CVE-2026-55008 Microsoft Exchange Server Spoofing 9.6 0.0086 More likely
High CVE-2026-55009 Microsoft Exchange Server Elevation of Privilege 7.8 0.0251 Exploitation Unlikely
High CVE-2026-45504 Microsoft Exchange Server Elevation of Privilege 8.8 0.0118 Exploitation Unlikely
High CVE-2026-55005 Microsoft Exchange Server Remote Code Execution 8.8 0.0101 Exploitation Less Likely
High CVE-2026-45583 Microsoft Exchange Server Remote Code Execution 7.5 0.0052 Exploitation Less Likely
High CVE-2026-45503 Microsoft Exchange Server Information Disclosure 8.1 0.0045 Exploitation Unlikely
High CVE-2026-47631 Microsoft Exchange Server Spoofing 8.1 0.0035 Exploitation Less Likely
High CVE-2026-55006 Microsoft Exchange Server Elevation of Privilege 7.8 0.0030 Exploitation Less Likely
Routine CVE-2026-45502 Microsoft Exchange Server Information Disclosure 5.0 0.1964 Exploitation Unlikely
Routine CVE-2026-45501 Microsoft Exchange Server Spoofing 6.5 0.0040 Exploitation Less Likely
Routine CVE-2026-45500 Microsoft Exchange Server Spoofing 6.1 0.0038 Exploitation Less Likely
Showing 1 to 11 of 11 1