Patch tracker / KB5123301

KB5123301: Skype Security Update (September 2026)

KB5123301 is a Critical security update for Skype, released 2026-09-08. It closes 10 CVEs with a maximum CVSS of 9.8. It is the 24th largest of the 54 updates Microsoft shipped that month, by CVEs closed.

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Update summary

Critical
2026-09-08
Released
10
CVEs fixed
9.8
Max CVSS v3
Critical
Severity
Deploy this cycle
Fixes 10 CVEs for Skype. No confirmed in-the-wild exploitation in this set today.

Fixes 10 CVEs. Most severe CVSS 9.8 (Critical). EPSS exploit probability up to 1.2%. Among the lower half of tracked Microsoft updates by EPSS exploit probability.

Senserva found thiswe track every release for this product line, so we can tell you this package is behind

A newer security update for Skype for Business Server 2015 CU13 has shipped since this one: KB5132779 (2026-10-13). For cumulative update families the newer package includes these fixes, so installing that one is usually the shorter path. Verify against your own update rings before you skip this package.

Senserva found thisno known issues as of our last check

We checked Microsoft's support article for KB5123301 on 2026-10-16 and it lists no known issues. Read the article before broad deployment; Microsoft adds issues as reports come in, and we re-check on every refresh.

Microsoft Update Catalog: download KB5123301Microsoft support article
Senserva AI Opinion and rich prompt for KB5123301

Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.

Full tracking and change history for KB5123301

Released
2026-09-08
Last changed
2026-09-26
Changes tracked
3

Senserva began recording day-to-day change history on 2026-07-07, and refreshes it several times a day. Release dates are historical where Microsoft publishes them; revision history is tracked from that date forward, so it does not include changes made before then.

Check if KB5123301 is installed

Elevated PowerShell. No output means it is not installed.

CVEs fixed by this update

Sorted exploited-first, then by CVSS. Every CVE links to its Senserva page with the full risk facts, references, and a ready-to-paste AI prompt.

CVESeverityCVSSEPSSExploited
CVE-2026-66302Critical9.81.2%No
CVE-2026-69646High8.31.2%No
CVE-2026-66304High7.51.2%No
CVE-2026-66307High7.51.2%No
CVE-2026-66305High7.11.2%No
CVE-2026-63523Medium6.51.2%No
CVE-2026-66303Medium6.51.2%No
CVE-2026-66306Medium6.51.2%No
CVE-2026-66308Medium6.51.2%No
CVE-2026-69642Medium6.51.2%No

Scope and sources

Affected products
Also released in September 2026

KB5122871

684 CVEs · Critical · exploited

KB5122876

620 CVEs · Critical · exploited

KB5122878

572 CVEs · Critical · exploited

KB5122880

608 CVEs · Critical · exploited

KB5122882

645 CVEs · Critical · exploited

KB5123065

398 CVEs · Critical · exploited

KB5123066

423 CVEs · Critical · exploited

KB5123099

559 CVEs · Critical · exploited

The full month, summarized: Microsoft Patch Tuesday.

Authoritative references
Official KB5123301 page (Microsoft Support)Microsoft Update CatalogMicrosoft Security Update Guide

See this and every Microsoft update ranked by real-world risk on the Microsoft Patch Tracker.

New to a term on this page? CVE, KB, KEV, CVSS, and EPSS are each explained once, on the Senserva security lexicon. Reference: Microsoft CVE and vulnerability management and the Microsoft patching guide.
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