Patch tracker / KB5129195

KB5129195: Windows 11 Version 25H2 for x64-based Security Update (August 2026)

KB5129195 is a High security update for Windows 11 Version 25H2 for x64-based, released 2026-08-11. It closes 1 CVE with a maximum CVSS of 7.8. It is the 51st largest of the 65 updates Microsoft shipped that month, by CVEs closed.

Update summary

High
2026-08-11
Released
1
CVEs fixed
7.8
Max CVSS v3
High
Severity
Deploy this cycle
Fixes 1 CVE for Windows 11 Version 25H2 for x64-based. No confirmed in-the-wild exploitation in this set today.

Fixes 1 CVE. Most severe CVSS 7.8 (High). EPSS exploit probability up to <1%. Among the lower half of tracked Microsoft updates by EPSS exploit probability.

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A newer security update for Windows 11 Version 25H2 for ARM64-based Systems has shipped since this one: KB5124008 (2026-09-08). 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.

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Microsoft documents 3 known issues with this update.

  • Domain-joined devices might lose their secure trust relationship with the domain
  • USB Audio Class 1.0 devices with error Code 10 or no output
  • File History might stop working after installing September 2026 Windows update

The full text, quoted from Microsoft

Microsoft Update Catalog: download KB5129195Microsoft support article
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Full tracking and change history for KB5129195

Released
2026-08-11
Last changed
2026-08-11
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 KB5129195 is installed

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Known issues, from Microsoft

Quoted from Microsoft's support article for KB5129195 (checked 2026-09-29). Verify against the article before acting.

Domain-joined devices might lose their secure trust relationship with the domain

Symptoms

After installing the September 8, 2026, Windows security update ( KB5124008 ), or later updates, some Credential Guard protected machine accounts might lose their secure channel with an on-premises Active Directory (AD) domain. Users might then be unable to sign in interactively with valid domain credentials and might receive a message stating that the trust relationship between the device and the domain failed. Offline sign-in using previously cached credentials might continue to work. AD replication and AD services on the domain controllers are not affected.

This issue occurs because KB5124008 and later updates enable the Machine Identity Isolation feature. While the update does not directly enable Machine Identity Isolation enforcement, it does cause Windows to begin honoring any existing or policy-provisioned settings that enabled Machine Identity Isolation enforcement. However, this feature is only supported for environments connected to domain controllers running at a Windows Server 2025 Domain Functional Level (DFL) and above. The feature should be disabled elsewhere. Any devices previously configured to use Machine Identity Isolation that are not connected to Windows Server 2025 domain controllers will experience this issue and will need to disable the feature.

Workaround

Important: This section contains information about modifying the registry. Before you modify the registry, back it up and make sure that you know how to restore it if a problem occurs. For more information, see How to back up and restore the registry in Windows .

To work around this issue, disable Machine Identity Isolation using the same management method that was used to enable it. Choose the applicable option below:

If Machine Identity Isolation was enabled by Intune policy, disable Machine Identity Isolation with Intune .

If Machine Identity Isolation was enabled by Group Policy, disable Machine Identity Isolation with Group Policy .

If Machine Identity Isolation was enabled directly in the registry, use these steps to disable it:

On the Windows 11, version 24H2 or 25H2 device, locate the following registry paths:

HKLM\SYSTEM\CurrentControlSet\Control\Lsa\MachineIdentityIsolation

HKLM\SOFTWARE\Policies\Microsoft\Windows\DeviceGuard\MachineIdentityIsolation

For either of these registry keys, if the value of MachineIdentityIsolation is set to 2 , change it to:

MachineIdentityIsolation = 0

After you disable Machine Identity Isolation, restart the device.

Then reset the secure channel ...

Windows release health for this update

From Microsoft's Windows release health for Windows 11, version 25H2; Windows 11, version 24H2, checked 2026-10-06. Microsoft's issue text is linked from each title.

Issues this update resolves

Other open issues on these Windows versions

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-2026-62721High7.81.2%No

Scope and sources

Affected products
Also released in August 2026

KB5120228

215 CVEs · Critical · exploited

KB5120229

195 CVEs · Critical · exploited

KB5120233

215 CVEs · Critical · exploited

KB5120238

183 CVEs · Critical · exploited

KB5120240

170 CVEs · Critical · exploited

KB5120242

195 CVEs · Critical · exploited

KB5120385

144 CVEs · Critical · exploited

KB5120386

139 CVEs · Critical · exploited

The full month, summarized: Microsoft Patch Tuesday.

Authoritative references
Official KB5129195 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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