Microsoft · Security update · December 9, 2025
KB5071873: December 2025 security update
KB5071873, released December 9, 2025, fixes 2 CVEs in Microsoft Exchange Server 2016 Cumulative Update 23. None of them is reported as exploited. Patch Radar priority: High.
High
CVEs closed
2
None rated Critical
Exploited
0
None reported
Exploitation more likely
0
Microsoft's assessment
Highest EPSS
0.0109
65th percentile
Priority of the 2 CVEs
Patch now 0
Urgent 0
High 1
Routine 1
Applies to
CVEs this fix closes
| Priority | CVE | Component | Impact | CVSS | EPSS | Exploitation |
|---|---|---|---|---|---|---|
| High | CVE-2025-64666 | Microsoft Exchange Server | Elevation of Privilege | 7.5 | 0.0109 | Exploitation Less Likely |
| Routine | CVE-2025-64667 | Microsoft Exchange Server | Spoofing | 5.3 | 0.0085 | Exploitation Unlikely |
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