Microsoft · Security update · September 8, 2026
KB5121609: September 2026 security update
KB5121609, released September 8, 2026, fixes 9 CVEs in Microsoft Exchange Server 2019 Cumulative Update 15. None of them is reported as exploited. Patch Radar priority: High.
High
CVEs closed
9
None rated Critical
Exploited
0
None reported
Exploitation more likely
0
Microsoft's assessment
Highest EPSS
0.0117
67th percentile
Priority of the 9 CVEs
Patch now 0
Urgent 0
High 6
Routine 3
Applies to
CVEs this fix closes
| Priority | CVE | Component | Impact | CVSS | EPSS | Exploitation |
|---|---|---|---|---|---|---|
| High | CVE-2026-69378 | Microsoft Exchange Server | Denial of Service | 7.5 | 0.0117 | Exploitation Less Likely |
| High | CVE-2026-69355 | Microsoft Exchange Server | Remote Code Execution | 8.8 | 0.0091 | Exploitation Less Likely |
| High | CVE-2026-69641 | Microsoft Exchange Server | Elevation of Privilege | 9.1 | 0.0086 | Exploitation Less Likely |
| High | CVE-2026-69356 | Microsoft Exchange Server | Spoofing | 9.3 | 0.0076 | Exploitation Less Likely |
| High | CVE-2026-55007 | Microsoft Exchange Server | Remote Code Execution | 8.1 | 0.0071 | Exploitation Less Likely |
| High | CVE-2026-69380 | Microsoft Exchange Server | Elevation of Privilege | 8.1 | 0.0069 | Exploitation Less Likely |
| Routine | CVE-2026-69361 | Microsoft Exchange Server | Spoofing | 6.5 | 0.0084 | Exploitation Less Likely |
| Routine | CVE-2026-69375 | Microsoft Exchange Server | Tampering | 6.5 | 0.0064 | Exploitation Less Likely |
| Routine | CVE-2026-69382 | Microsoft Exchange Server | Information Disclosure | 5.9 | 0.0047 | Exploitation Less Likely |
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