Patch tracker / KB5123731

KB5123731: Dynamics 365 Customer Engagement V9.1 Security Update (September 2026)

KB5123731 is a High security update for Dynamics 365 Customer Engagement V9.1, released 2026-09-08. It closes 1 CVE with a maximum CVSS of 8.8. It is the 41st largest of the 54 updates Microsoft shipped that month, by CVEs closed.

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Update summary

High
2026-09-08
Released
1
CVEs fixed
8.8
Max CVSS v3
High
Severity
Deploy this cycle
Fixes 1 CVE for Dynamics 365 Customer Engagement V9.1. No confirmed in-the-wild exploitation in this set today.

Fixes 1 CVE. Most severe CVSS 8.8 (High). EPSS exploit probability up to <1%. Among the lower half of tracked Microsoft updates by EPSS exploit probability.

Microsoft Update Catalog: download KB5123731Microsoft support article
Senserva AI Opinion and rich prompt for KB5123731

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

Full tracking and change history for KB5123731

Released
2026-09-08
Last changed
2026-09-10
Changes tracked
2

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 KB5123731 is installed

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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-2026-77908High8.8<1%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 KB5123731 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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