Patch tracker / KB5078738

KB5078738: Windows 11 version 26H1 for x64-based Security Update (March 2026)

KB5078738 is a High security update for Windows 11 version 26H1 for x64-based , released 2026-03-10. It closes 1 CVE with a maximum CVSS of 7.5. It is the 32nd largest of the 38 updates Microsoft shipped that month, by CVEs closed.

Update summary

High
2026-03-10
Released
1
CVEs fixed
7.5
Max CVSS
High
Severity
Deploy this cycle
Fixes 1 CVE for Windows 11 version 26H1 for x64-based . No confirmed in-the-wild exploitation in this set today.

Fixes 1 CVE. Most severe CVSS 7.5 (High). 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 Windows 11 Version 26H1 for ARM64-based Systems has shipped since this one: KB5082126 (2026-04-14). 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.

Microsoft Update Catalog: download KB5078738Microsoft support article
Senserva AI Opinion for KB5078738

KB5078738 patches a single flaw, CVE-2026-23674, rated High with a CVSS of 7.5, across Windows 11 version 26H1 for ARM64 and x64 plus Windows Server 2019 Server Core. The mix here is unusual: a brand new client OS release sits alongside a headless Server Core install, so both your newest desktops and your minimal server footprint need the same fix. Exploitation pressure is currently low, with EPSS at 1 percent and no listing in CISA KEV or ransomware campaigns.

Do this: Deploy KB5078738 through your normal patch ring, but confirm Server Core 2019 hosts are included since they are easy to miss in desktop-focused rollouts.

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

Senserva AI Opinion and rich prompt for KB5078738

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

Full tracking and change history for KB5078738

Released
2026-03-10
Last changed
2026-03-10
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 KB5078738 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-2026-23674High8.84.7%No

Scope and sources

Affected products
Also released in March 2026

KB5002843

3 CVEs · High

KB5002845

4 CVEs · High

KB5002850

4 CVEs · High

KB5077464

2 CVEs · High

KB5077465

2 CVEs · High

KB5077466

3 CVEs · High

KB5077468

3 CVEs · High

KB5077469

2 CVEs · High

The full month, summarized: Microsoft Patch Tuesday.

Authoritative references
Official KB5078738 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.