CVE-2026-66307: Microsoft Skype For Business Server

High severity, CVSS 7.5. EPSS: 1.2% chance of exploitation in the next 30 days.

Integer underflow (wrap or wraparound) in Skype for Business allows an unauthorized attacker to deny service over a network.

Affected products

• Microsoft Skype For Business Server: version 2015 only; version 2019 only
• Microsoft Skype For Business Server Subscription Edition: version 7.0.2046.849 only

Published 2026-09-08. Last modified 2026-09-16.