Summary
- Microsoft published an MSRC blog about the response to compromised eMudhra intermediate certificate authority keys.
- Windows and Microsoft Edge trust lists are being updated as part of the response.
- Administrators managing disconnected devices or devices that do not receive automatic certificate trust updates should review the guidance and apply the relevant Windows updates.
- Out-of-band Windows updates are available in the Microsoft Update Catalog for multiple supported Windows client and server versions.
Primary Service: Windows
Admin Impact: Medium
User Impact: Low
Release Start: 27 Oct 2026
Release End: 27 Oct 2026
Services: Edge, Windows
Category: Prevent or fix issues
Tags: Admin Action
History
10/27/2026 Item Added to Message Center
Microsoft Message
Microsoft has published a new blog post outlining our response to the compromise of eMudhra intermediate certificate authority keys, including changes to the Windows and Microsoft Edge trust lists.
The Windows out-of-band updates are now available in the Microsoft Update Catalog. Administrators managing disconnected devices, or devices that don’t receive automatic certificate trust updates, can find more context and recommended steps in Microsoft’s response to compromised eMudhra certificate authority keys.
The following Windows updates are now available:
- Windows 11, version 26H1: KB5134134
- Windows 11, versions 26H2, 25H2, and 24H2: KB5134133
- Windows 11, version 23H2: KB5134130
- Windows Server 2025: KB5134137
- Windows Server 2022: KB5134140
- Windows 10, version 22H2 and Windows 10 Enterprise LTSC 2021: KB5134125
- Windows 10 Enterprise LTSC 2019 and Windows Server 2019: KB5134124
- Windows Server 2016: KB5134123