CVE-2026-66307

Skype for Business and Lync Denial of Service Vulnerability

Published Sep 8, 2026 CVSS 3.1 · 7.5 High EPSS 1.2% KEV · Not listed
Description
Integer underflow (wrap or wraparound) in Skype for Business allows an unauthorized attacker to deny service over a network.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
First Time appeared Microsoft skype For Business Server
CPEs cpe:2.3:a:microsoft:skype_for_business_server:2015:cumulative_update_13:*:*:*:*:*:*
cpe:2.3:a:microsoft:skype_for_business_server:2015:cumulative_update_13_hotfix_2:*:*:*:*:*:*
cpe:2.3:a:microsoft:skype_for_business_server:2019:cumulative_update_8:*:*:*:*:*:*
cpe:2.3:a:microsoft:skype_for_business_server:2019:cumulative_update_8_hotfix1:*:*:*:*:*:*
cpe:2.3:a:microsoft:skype_for_business_server:2019:cumulative_update_8_hotfix2:*:*:*:*:*:*
cpe:2.3:a:microsoft:skype_for_business_server_subscription_edition:7.0.2046.849:*:*:*:*:*:*:*
Vendors & Products Microsoft skype For Business Server
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description Integer underflow (wrap or wraparound) in Skype for Business allows an unauthorized attacker to deny service over a network.
Title Skype for Business and Lync Denial of Service Vulnerability
First Time appeared Microsoft
Microsoft skype For Business Server 2015
Microsoft skype For Business Server 2019
Microsoft skype For Business Server Subscription Edition
Weaknesses CWE-191
CPEs cpe:2.3:a:microsoft:skype_for_business_server_2015:*:cu13:*:*:*:*:*:*
cpe:2.3:a:microsoft:skype_for_business_server_2019:*:cu8:*:*:*:*:*:*
cpe:2.3:a:microsoft:skype_for_business_server_subscription_edition:*:cu1:*:*:*:*:*:*
Vendors & Products Microsoft
Microsoft skype For Business Server 2015
Microsoft skype For Business Server 2019
Microsoft skype For Business Server Subscription Edition
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
microsoft
Published
Updated
Nov 10, 2026, 9:38 PM
Reserved
Jul 24, 2026, 6:06 PM
Status
Analyzed
Published
Sep 8, 2026, 7:18 PM
Modified
Sep 16, 2026, 7:24 PM