What is CVE-2026-66307?

CVE-2026-66307 is a high-severity vulnerability in Microsoft Skype For Business Server 2015 Cu13, classified under Integer Underflow. CVSS score: 7.5/10. Published 2026-09-08.

How severe is CVE-2026-66307?

High severity. CVSS v3 base score is 7.5 out of 10.

Integer overflow in Microsoft Skype For Business Server 2015 Cu13

CVE-2026-66307

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

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

Affected products

Microsoft Skype For Business Server 2015 Cu13

Weakness classification (CWE)

CWE-191 — Integer Underflow

References

secure@microsoft.com (vendor-advisory, patch)

Frequently asked questions

What is CVE-2026-66307?: CVE-2026-66307 is a high-severity vulnerability in Microsoft Skype For Business Server 2015 Cu13, classified under Integer Underflow. CVSS score: 7.5/10. Published 2026-09-08.
How severe is CVE-2026-66307?: High severity. CVSS v3 base score is 7.5 out of 10.