CVE record · CVE-2026-66307

Skype for Business and Lync Denial of Service Vulnerability

CVSS 7.5 HighEPSS 0.012 · 67th percentile

Published by the CVE Program (CNA: microsoft) at 8 Sept 2026, 18:39 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. This CVE names a vendor and product rather than a package, so the lockfile check doesn’t match it.

Affected products, as the CNA wrote them
Vendor	Product	Versions
Microsoft	Skype for Business Server 2015 CU13	affected 9319.0 to before 6.0.9319.885 custom
Microsoft	Skype for Business Server 2019 CU8	affected 2046.0 to before 7.0.2046.569 custom
Microsoft	Skype for Business Server Subscription Edition CU1	affected 2046.0 to before 7.0.2046.879 custom

Identifiers: CVE-2026-66307
CNA: microsoft
Weakness (CWE): CWE-191
Tags: Microsoft Skype for Business Server 2015 CU13
Microsoft Skype for Business Server 2019 CU8
Microsoft Skype for Business Server Subscription Edition CU1
Memory corruption
Published: 8 Sept 2026
Updated: 31 Oct 2026

Not analysed yet

We haven’t published our own analysis of this CVE. If a person reviews it, this page will say what’s affected and what has to be true for it to matter.

Severity and exploitation

Score	Rating	CVSS	Vector	Source
7.5	High	3.1	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	CNA (microsoft)

CISA KEV Not listed.
EPSS 0.012, the 67th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

8 Sept 2026, 18:39 UTC Confirmed by the CVE List
31 Oct 2026, 16:26 UTC First seen by agentprime

Sources

References from the CNA

msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66307 vendor-advisorypatch

Facts on this page come from the CVE List as the CNA published them, with CVSS from the sources named above, CISA KEV and FIRST EPSS. Vendors, products and versions are shown as the CNA wrote them. We don’t reproduce the CVE’s description.