Microsoft · Security update · September 8, 2026
KB5123300: September 2026 security update
KB5123300, released September 8, 2026, fixes 10 CVEs across 2 products. None of them is reported as exploited. Patch Radar priority: Urgent.
Urgent
CVEs closed
10
1 rated Critical
Exploited
0
None reported
Exploitation more likely
0
Vendor assessment
Highest EPSS
0.0117
67th percentile
Priority of the 10 CVEs
Patch now 0
Urgent 1
High 4
Routine 5
Applies to
CVEs this fix closes
| Priority | CVE | Component | Impact | CVSS | EPSS | Exploitation |
|---|---|---|---|---|---|---|
| Urgent | CVE-2026-66302 | Skype for Business | Remote Code Execution | 9.8 | 0.0097 | Exploitation Less Likely |
| High | CVE-2026-66307 | Skype for Business | Denial of Service | 7.5 | 0.0117 | Exploitation Less Likely |
| High | CVE-2026-66304 | Skype for Business | Information Disclosure | 7.5 | 0.0097 | Exploitation Less Likely |
| High | CVE-2026-66305 | Skype for Business | Spoofing | 7.1 | 0.0053 | Exploitation Less Likely |
| High | CVE-2026-69646 | Skype for Business | Spoofing | 8.3 | 0.0032 | Exploitation Less Likely |
| Routine | CVE-2026-66303 | Skype for Business | Denial of Service | 6.5 | 0.0114 | Exploitation Less Likely |
| Routine | CVE-2026-66308 | Skype for Business | Denial of Service | 6.5 | 0.0114 | Exploitation Less Likely |
| Routine | CVE-2026-66306 | Skype for Business | Information Disclosure | 6.5 | 0.0092 | Exploitation Less Likely |
| Routine | CVE-2026-63523 | Skype for Business | Spoofing | 6.5 | 0.0055 | Exploitation Less Likely |
| Routine | CVE-2026-69642 | Skype for Business | Spoofing | 6.5 | 0.0041 | Exploitation Unlikely |
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