Microsoft · Security update · September 8, 2026

KB5123287: September 2026 security update

KB5123287, 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
Microsoft's 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

PriorityCVEComponentImpactCVSSEPSSExploitation
Urgent CVE-2026-66302 Skype for BusinessRemote Code Execution9.8 0.0097 Exploitation Less Likely
High CVE-2026-66307 Skype for BusinessDenial of Service7.5 0.0117 Exploitation Less Likely
High CVE-2026-66304 Skype for BusinessInformation Disclosure7.5 0.0097 Exploitation Less Likely
High CVE-2026-66305 Skype for BusinessSpoofing7.1 0.0053 Exploitation Less Likely
High CVE-2026-69646 Skype for BusinessSpoofing8.3 0.0032 Exploitation Less Likely
Routine CVE-2026-66303 Skype for BusinessDenial of Service6.5 0.0114 Exploitation Less Likely
Routine CVE-2026-66308 Skype for BusinessDenial of Service6.5 0.0114 Exploitation Less Likely
Routine CVE-2026-66306 Skype for BusinessInformation Disclosure6.5 0.0092 Exploitation Less Likely
Routine CVE-2026-63523 Skype for BusinessSpoofing6.5 0.0055 Exploitation Less Likely
Routine CVE-2026-69642 Skype for BusinessSpoofing6.5 0.0041 Exploitation Unlikely
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