What is CVE-2026-66303?

CVE-2026-66303 is a security advisory published by Microsoft Security Response Center (MSRC) with High severity. Skype for Business and Lync Denial of Service Vulnerability

Which CVE IDs does CVE-2026-66303 cover?

CVE-2026-66303 covers the following CVE IDs: CVE-2026-66303. Each CVE has its own detail page on EchelonGraph Pulse with the synthesized EG score.

What is the CVSS v3 score of CVE-2026-66303?

CVE-2026-66303 has a CVSS v3 base score of 6.5, published by Microsoft Security Response Center (MSRC).

Which products are affected by CVE-2026-66303?

CVE-2026-66303 affects 3 products, including: Skype for Business Server 2015 CU13; Skype for Business Server 2019 CU8; Skype for Business Server Subscription Edition CU1.

CVE-2026-66303HighCVSS 6.5

Skype for Business and Lync Denial of Service Vulnerability

Vendor

Microsoft Security Response Center (MSRC)

Published

September 11, 2026

Last Modified

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🔗 CVE IDs covered (1)

CVE-2026-66303 →

📋 Description

Null pointer dereference in Skype for Business allows an authorized attacker to deny service over a network.

🎯 Affected products3

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

✅ Remediation

KB5123301 (Security Update) — fixed build 6.0.9319.885 KB5123300 (Security Update) — fixed build 7.0.2046.569 KB5123287 (Security Update) — fixed build 7.0.2046.879

🔗 References (5)

advisoryhttps://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66303
referencehttps://support.microsoft.com/help/5123301
referencehttps://support.microsoft.com/help/5123300
patchhttps://www.microsoft.com/en-us/download/details.aspx?id=108824
referencehttps://support.microsoft.com/help/5123287