Patch tracker / KB5078943

KB5078943: Microsoft Dynamics 365 version 9.1 Security Update (May 2026)

KB5078943 is a Critical security update for Microsoft Dynamics 365 version 9.1, released 2026-05-12. It closes 3 CVEs with a maximum CVSS of 9.9. It is the 18th largest of the 55 updates Microsoft shipped that month, by CVEs closed.

Update summary

Critical
2026-05-12
Released
3
CVEs fixed
9.9
Max CVSS
Critical
Severity
Deploy this cycle
Fixes 3 CVEs for Microsoft Dynamics 365 version 9.1. No confirmed in-the-wild exploitation in this set today.

Fixes 3 CVEs. Most severe CVSS 9.9 (Critical). EPSS exploit probability up to 1.2%. Among the lower half of tracked Microsoft updates by EPSS exploit probability.

Microsoft Update Catalog: download KB5078943Microsoft support article
Senserva AI Opinion for KB5078943

KB5078943 patches three CVEs in on-premises Dynamics 365 versions 9.1 and 9.0, one rated Critical at CVSS 9.9. Because these are self-hosted Dynamics deployments, the responsibility for applying this fix falls entirely on your team rather than Microsoft's cloud operations. The 9.9 score signals a flaw requiring little privilege or user interaction, though EPSS currently estimates only a 1 percent chance of exploitation in the near term and none of the CVEs appear in CISA KEV.

Do this: Schedule and apply KB5078943 to all on-premises Dynamics 365 version 9.1 and 9.0 servers, prioritizing any instances reachable from outside your network.

AI-generated from public data, 2026-07-21. Verify against the vendor advisory before acting.

Senserva AI Opinion and rich prompt for KB5078943

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

Full tracking and change history for KB5078943

Released
2026-05-12
Last changed
2026-05-12
Changes tracked
1

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 KB5078943 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-2026-33103Critical9.91.2%No
CVE-2026-42833Critical9.91.2%No
CVE-2026-42898Critical9.91.2%No

Scope and sources

Affected products
Also released in May 2026

KB5002863

9 CVEs · High · exploited

KB5002868

9 CVEs · High · exploited

KB5002870

9 CVEs · High · exploited

KB5087420

56 CVEs · Critical

KB5087424

56 CVEs · Critical

KB5087470

39 CVEs · Critical

KB5087471

42 CVEs · Critical

KB5087537

47 CVEs · Critical

The full month, summarized: Microsoft Patch Tuesday.

Authoritative references
Official KB5078943 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.
Provided as is, without warranty; verify against the vendor advisory before acting. Data notice and terms.