High MSRC-CVE-2026-66307 1 CVE

Skype for Business and Lync Denial of Service Vulnerability

Published Sep 8, 2026 · Updated Sep 8, 2026

Vendor: Microsoft

Summary

Impact: Denial of Service. Microsoft rating: Important. Not known to be exploited — Exploitation Less Likely. Customer action: Required.

Details

Security updates
6.0.9319.885 — https://support.microsoft.com/help/5123301
7.0.2046.879 — https://support.microsoft.com/help/5123287
7.0.2046.569 — https://support.microsoft.com/help/5123300

Vulnerabilities 1

High 7.5

CVE-2026-66307

Skype for Business and Lync Denial of Service Vulnerability

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

Microsoft Skype for Business Server 2015 CU13 Skype for Business Server 2019 CU8 Skype for Business Server Subscription Edition CU1

Sep 8, 2026

Revision history

2026-09-08 #1
Information published.

References

CVE-2026-66307 Skype for Business and Lync Denial of Service Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66307
Microsoft Exploitability Index
https://www.microsoft.com/en-us/msrc/exploitability-index?rtc=1
Microsoft Support Lifecycle
https://support.microsoft.com/lifecycle
Common Vulnerability Scoring System
https://www.first.org/cvss