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Windows 10 1809 Windows 10 1809 Security update
Patch Tuesday

KB5087538

KB5087538: Cumulative update for Windows 10, version 1809, May 2026. Secure Boot certificate coverage expands; sign-in errors fixed

In short

The update expands Secure Boot certificate targeting and fixes Microsoft-account sign-in errors and a Remote Desktop display warning. Secure Boot certificates have started expiring in June 2026, so Microsoft recommends preparing devices.

Does it affect you? Applies to: Devices running Windows 10 Enterprise LTSC 2019, version 1809.

Build
17763.8755
Security
52 fixed · 3 critical
Restart
Required

Microsoft publishes separate notes for this KB for Windows Server.

What changes

Fixes 2 changes

Remote Desktop security warnings

Verified in package

For: Devices using multiple monitors with different display scaling

  • The Remote Desktop Connection security warning dialog no longer renders incorrectly on multi-monitor setups with different display scaling.1
    The issue might occur after installing a Windows security update released on or after April 14, 2026.

Sign-In

For: Some users signing in to apps with a Microsoft account

  • Some users can sign in to Microsoft-account apps again instead of seeing a “no Internet” error despite a working connection.2
    The issue could occur after installing a Windows update released on or after March 10, 2026, and could block access to Microsoft services and apps such as Microsoft Teams.

Improvements 2 changes

Secure Boot

Gradual rollout Verified in package

For: Devices eligible to receive new Secure Boot certificates automatically

  • More eligible devices can receive new Secure Boot certificates automatically after demonstrating sufficient successful update signals.3
    Adds high-confidence device targeting data to Windows quality updates, increasing coverage while maintaining a controlled, phased rollout.

Daylight Savings Time

For: Devices using Egypt’s time settings

  • Daylight saving time in Egypt is updated to support the government’s 2023 change order.4

New features 2 changes

Secure Boot

Verified in package 2 items
  • Windows Security can report Secure Boot states dynamically.5
    Adds dynamic status reporting for Secure Boot states in Windows Security App.
  • Eligible devices get a SecureBoot folder containing sample scripts for checking certificate status and automating deployment.6
    The scripts are intended for organizations with IT professionals managing device fleets and support safe rollout in an Active Directory environment.

Technical details

Data sheet · Security · Downloads · Components Click to collapse or expand

Data sheet

Released
2026-05-12
Classification
Security Updates
Type
Cumulative update
Restart
Required
Replaces
KB5091573, KB5082123, KB5078752, KB5075904
+18 earlier KB5078131, KB5077795, KB5073723, KB5074975, KB5071544, KB5068791, KB5066586, KB5065428, KB5066187, KB5063877, KB5062557, KB5060531, KB5061978, KB5058392, KB5059091, KB5058922, KB5050008, KB5037425
Replaced by
KB5094123
VersionBuildChannel
1809 17763.8755 General availability

Security

52 vulnerabilities fixed
3 critical 49 important
VulnerabilitySeverityCVSS
CVE-2026-40403
Windows Graphics Component Remote Code Execution Vulnerability
 Critical 8.8
CVE-2026-35421
Windows GDI Remote Code Execution Vulnerability
 Critical 7.8
CVE-2026-32161
Windows Native WiFi Miniport Driver Remote Code Execution Vulnerability
 Critical 7.5

The table lists the 3 exploited, publicly disclosed or critical vulnerabilities. See all 52 vulnerabilities →

Updated components

1,994 files changed since the previous update for the same versions.

Top changed componentsFiles
Graphics and display19
Networking16
Secure Boot15
Security and sign-in11
Hyper-V and virtualization7
Storage and file systems7
File Explorer and shell6
Kernel6
Audio5
Remote Desktop4
Printing2
Settings2

Verified in package: changed files confirm Remote Desktop security warnings, Secure Boot.

Sources

Updated
Cited passages from Microsoft's official notes (6)
  1. 1. Fixed: The Remote Desktop Connection security warning dialog might render incorrectly in multi-monitor configurations with different display scaling settings. support.microsoft.com
  2. 2. Even when the device has a working Internet connection, a “no Internet” error appears during sign in and prevents access to Microsoft services and apps such as Microsoft Teams. support.microsoft.com
  3. 3. With this update, Windows quality updates include additional high confidence device targeting data, increasing coverage of devices eligible to automatically receive new Secure Boot certificates. support.microsoft.com
  4. 4. Update for Arab Republic of Egypt to support the government DST change order in 2023. support.microsoft.com
  5. 5. This update enables dynamic status reporting for Secure Boot states in Windows Security App. support.microsoft.com
  6. 6. This update adds a new SecureBoot folder under C:\Windows on eligible devices. support.microsoft.com
Checked automatically: 8 of 8 checks passed, 6 quoted passages · compared with Microsoft's page on Sep 25, 2026
  • Quotes found in the official pages: passed
  • Numbers found in the sources: passed
  • Vulnerabilities from the dossier only: passed
  • Links to allowed domains only: passed
  • Every official change covered: passed
  • Readable plain text: passed
  • Changes confirmed by the file list: passed
  • Sources agree: passed

A second AI read the text against the sources: correctness 4/5, clarity 4/5, completeness 4/5. How we work

Published by The Update Bureau. Written with AI from Microsoft's own documents, checked by rules and a second AI. How we work · Report a mistake