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The Update Bureau

Monthly Patch Briefing

May 2026

63 updates released this month across 8 product lines · 35 Patch Tuesday · 5 previews .

Release volume

63 updates released

3 more than April (60), vs 50/mo in 2026.

May 2026
63
Apr 2026
60
2026 average
50/mo

Security flaws fixed

83 vulnerabilities

-68 flaws compared to April (151).

May 2026
83
Apr 2026
151
2026 average
88/mo

Critical & urgent

8 critical

5 critical in April.

May critical
8
Apr critical
5
2026 average
4/mo

2026 Year-to-Date Trend

439 security flaws fixed across 250 updates in 2026

20 critical flaws and 7 exploited zero-days patched across the 5 published months of 2026.

Distinct security flaws fixed per month Jan – May 2026
May 2026
.NET Framework
Monthly security update
3 previews 2 fixed
  • .NET 3.5 / 4.8.1 · Windows 11 26H1 KB5087055 → 3.5, 4.8.1
  • .NET 3.5 / 4.8.1 · Windows 11 25H2, Windows Server 2025 KB5087051 → 3.5, 4.8.1
  • .NET 3.5 / 4.8.1 · Windows 11 24H2 KB5087054 → 3.5, 4.8.1
  • .NET 3.5 / 4.8.1 · Windows 11 23H2 KB5087058 → 3.5, 4.8.1
+7 more KB5087053 3.5, 4.8.1 · KB5087059 3.5, 4.8.1 · KB5087064 3.5, 4.8 · KB5087068 3.5, 4.8 · KB5087066 3.5, 4.8 · KB5087065 4.8 · KB5087061 3.5, 4.7.2
2 fixed · 0 critical
Exchange Server
Monthly security update
0 fixed
  • No Patch Tuesday security update this month —
0 fixed · 0 critical

Vulnerabilities fixed, by version

Product Version Monthly update & build Critical Important Total
Windows 11
Windows 11, version 26H1 KB5089548 28000.2113 4 58 62
Windows 11
Windows 11, version 25H2 KB5089549 26200.8457 4 57 61
Windows 11
Windows 11, version 24H2 KB5089549 26100.8457 4 57 61
Windows 11
Windows 11, version 23H2 KB5087420 22631.7079 5 51 56
Windows 10
Windows 10 Enterprise LTSC 2019 KB5087538 17763.8755 3 49 52
Windows 10
Windows 10 Enterprise LTSB 2016 KB5087537 14393.9140 3 41 44
Windows 10
Windows 10, version 22H2 KB5087544 19045.7291 3 51 54
Windows 10
Windows 10 Enterprise LTSC 2021 KB5087544 19044.7291 3 51 54
Windows Server
Windows Server 2025 KB5087539 26100.32860 5 61 66
Windows Server
Windows Server 2022 KB5087545 20348.5139 5 53 58
Windows Server
Windows Server 2019 KB5087538 17763.8755 4 51 55
Windows Server
Windows Server 2016 KB5087537 14393.9140 4 43 47
.NET Framework
.NET Framework 4.8.1 KB5087055 4.8.9335.0 · 2 2
.NET Framework
.NET Framework 4.8 KB5087064 4.8.4802.0 · 2 2
.NET Framework
.NET Framework 4.7.2 KB5087061 4.7.4142.0 · 2 2
.NET Framework
.NET Framework 3.5 KB5087055 · 2 2
SQL Server
SQL Server 2025 KB5089899 17.0.4040.1 · 1 1
SQL Server
SQL Server 2022 KB5089900 16.0.4252.3 · 1 1
SQL Server
SQL Server 2019 KB5090407 15.0.4470.1 · 1 1
SQL Server
SQL Server 2017 KB5090354 14.0.3530.2 · 1 1
SQL Server
SQL Server 2016 KB5089270 13.0.7085.1 · 1 1
SharePoint Server
SharePoint Server Subscription Edition KB5002863 16.0.19725.20280 2 7 9
SharePoint Server
SharePoint Server 2019 KB5002870 16.0.10417.20128 2 7 9
SharePoint Server
SharePoint Server 2016 KB5002868 16.0.5552.1002 2 7 9
Office Online Server
Office Online Server KB5002871 16.0.10417.20128 · 3 3

All updates

All updates:
  • Windows 11 · Future platforms
    Windows 11 Windows 11 Insider Future platforms Insider Preview
    Experimental Channel
    Build 29599.1000

    Task Manager CPU speed display and Microsoft account sign-in fix

    Build 29599.1000 is for Insiders in the Canary 29500 Series Channel, though some may not yet have transitioned to Experimental (Future Platforms). It fixes a misleading internet message during Microsoft account sign-in and improves CPU speed display for virtual machines.

    Changes 2 improved · 1 fix
  • Windows 11 · Future platforms
    Windows 11 Windows 11 Insider Future platforms Insider Preview
    Experimental Channel
    Build 29595.1000

    Windows platform moves to a new active development build

    Build 29595.1000 carries platform changes as Windows moves to a new active development build. The notes apply to Canary 29500 Series Insiders, who are transitioning to the Experimental channel.

    Changes 1 improved
  • Windows 11 · 26H1
    Windows 11 Windows 11 Insider 26H1 Insider Preview
    Experimental Channel
    Build 28020.2207

    Preview build 28020.2207 for the Experimental Channel

    Includes a small number of minor bug fixes and improvements, but the notes do not identify them.

    Changes 1 improved · 1 fix
  • Windows 11 · 26H2
    Windows 11 Windows 11 Insider 26H2 Insider Preview
    Experimental Channel
    Build 26300.8553

    Start menu controls and substring search for files

    Experimental Channel Insiders get more Start menu customization, file search by part of a name or its contents, and taskbar changes, including a fix for visual issues in alternate positions.

    Changes 1 new · 6 improved · 2 fixes
  • Windows 11 · 25H2
    Windows 11 Windows 11 Insider 25H2 Insider Preview
    Beta Channel
    Build 26220.8544

    Search finds name fragments; printer setup gets a default-method toggle

    Beta Channel Insiders get search that finds files by parts of their names or content, plus a setting to control the default printer installation method.

    Changes 1 new · 1 improved
  • Windows 11 · 26H1
    Windows 11 26H1 Windows 11 26H1 Optional preview
    Preview
    KB5089570

    Shared Audio arrives; File Explorer and system reliability improve

    Adds Shared Audio, Xbox mode, new input and taskbar features, and improves several Windows components. It also fixes a File Explorer dark-mode flash and reduces Microsoft Store download and install errors.

    Build 28000.2179
    Replaced by KB5095051 →
  • Windows 11 · 24H2, 25H2
    Windows 11 24H2 / 25H2 Windows 11 24H2 / 25H2 Optional preview
    Preview
    KB5089573

    Shared Audio arrives; Secure Boot coverage expands

    Adds features including Shared Audio and camera controls, and addresses an installation failure for devices with little free EFI System Partition space. It also improves automatic delivery of updated Secure Boot certificates.

    Builds 26100.8524 26200.8524
    Replaced by KB5094126 →
  • .NET Framework · 3.5, 4.8.1
    .NET Framework 3.5 / 4.8.1 .NET Framework 3.5 / 4.8.1 for Windows 11 26H1 Optional preview
    Preview
    KB5092431

    HttpWebRequest hangs and x86 debugger values corrected

    Addresses cases where secure web requests hang and where Visual Studio's x86 debugger reports some floating-point values incorrectly.

    Build 4.8.9337.0
    Replaced by KB5101002 →
  • .NET Framework · 3.5, 4.8.1
    .NET Framework 3.5 / 4.8.1 .NET Framework 3.5 / 4.8.1 for Windows 11 25H2 Optional preview
    Preview
    KB5092427

    Hanging secure requests and incorrect debugger values addressed

    Addresses hanging synchronous web requests in certain secure-connection setups and incorrect floating-point values in Visual Studio’s x86 native debugger.

    Builds 4.8.9337.0 2.0.50727.9181
    Replaced by KB5100998 →
  • .NET Framework · 3.5, 4.8.1
    .NET Framework 3.5 / 4.8.1 .NET Framework 3.5 / 4.8.1 for Windows 11 24H2 Optional preview
    Preview
    KB5092430

    Hanging secure requests and debugger values addressed

    Addresses cases where secure HTTP requests could hang and floating-point values could be reported incorrectly in Visual Studio’s x86 native debugger.

    Builds 4.8.9336.0 2.0.50727.9181
    Replaced by KB5101001 →
  • Windows 11 · Future platforms
    Windows 11 Windows 11 Insider Future platforms Insider Preview
    Experimental Channel
    Build 29591.1000

    Shared audio and more control over Windows Update

    This build for Insiders in the Canary 29500 series adds shared audio and new Windows Update controls, and changes when Storage asks for administrator approval.

    Changes 2 new · 4 improved
  • Windows 11 · 26H1
    Windows 11 Windows 11 Insider 26H1 Insider Preview
    Experimental Channel
    Build 28020.2149

    Dev Drive size controls and improved Greek and Cyrillic text

    Build 28020.2149 for the Experimental Channel gradually improves desktop reliability, Dev Drive sizing, and Greek and Cyrillic text rendering. The notes also mark a Reset this PC issue as fixed.

    Changes 3 improved · 1 fix
  • Windows 11 · 26H2
    Windows 11 Windows 11 Insider 26H2 Insider Preview
    Experimental Channel
    Build 26300.8497

    HID braille support and screen tint for accessibility

    Adds HID braille support, screen tint and Voice Isolation, and includes fixes for input, Explorer and other issues.

    Changes 4 new · 3 improved · 5 fixes
  • Windows 11 · 25H2
    Windows 11 Windows 11 Insider 25H2 Insider Preview
    Beta Channel
    Build 26220.8491

    Voice Isolation and screen tint come to accessibility settings

    Beta Channel Insiders get Voice Isolation in Voice Access and a screen tint setting, alongside fixes for Explorer crashes, duplicate Energy Saver controls, and unexpected muting.

    Changes 2 new · 4 fixes
  • SQL Server · CU5
    SQL Server 2025 CU5 SQL Server 2025 CU5 Cumulative update
    KB5084896

    XXE and SQL injection flaws fixed; lock-memory control added

    Fixes seven issues, including an XXE vulnerability in the Web Service Task and a SQL injection vulnerability. It also adds a setting to limit lock-manager cache memory.

    Build 17.0.4045.5
    Known issues 2 open
    Replaced by KB5093421 →
  • SQL Server · CU25
    SQL Server 2022 CU25 SQL Server 2022 CU25 Cumulative update
    KB5081477

    Web Service Task blocks file access through WSDL endpoints

    Includes 12 fixes for SQL Server 2022, including a Web Service Task fix that blocks unauthorized file access through WSDL endpoints. It also leaves two known issues open.

    Build 16.0.4255.1
    Known issues 2 open
    Replaced by KB5101347 →
  • Windows 11 · Future platforms
    Windows 11 Windows 11 Insider Future platforms Insider Preview
    Experimental Channel
    Build 29585.1000

    Voice typing animations move onto the dictation key

    Updates voice typing on the touch keyboard and includes printer-driver changes and fixes. The notes apply to Canary 29500 series Insiders, who may not yet have moved to Experimental (Future Platforms).

    Changes 4 improved · 1 fix
  • Windows 11 · 26H1
    Windows 11 Windows 11 Insider 26H1 Insider Preview
    Experimental Channel
    Build 28020.2134

    More control over Windows updates and better SSDP reliability

    Adds update controls and improves SSDP notification reliability. Resetting a PC may get stuck with a local reset; the notes recommend cloud download.

    Changes 5 improved
  • Windows 11 · 26H2
    Windows 11 Windows 11 Insider 26H2 Insider Preview
    Experimental Channel
    Build 26300.8493

    Taskbar moves to four screen edges and gets a smaller size

    Adds taskbar position and size options, updates Widgets and Windows Search, and includes reliability fixes. The new taskbar options are rolling out gradually.

    Changes 3 new · 10 improved · 2 fixes
  • Windows 11 · 25H2
    Windows 11 Windows 11 Insider 25H2 Insider Preview
    Beta Channel
    Build 26220.8474

    Spanish and French dictation, plus a Recycle Bin Properties fix

    Adds Fluid Dictation in Spanish and French, fixes File Explorer Properties, and improves SSDP and DISM reliability. Resetting your PC may still get stuck.

    Changes 1 new · 3 improved · 1 fix
  • Windows 11 · 26H1
    Windows 11 26H1 Windows 11 26H1 Security update
    KB5089548

    Critical DNS and graphics flaws addressed

    The update addresses 62 security vulnerabilities, including four critical ones, and improves network-device discovery and compatibility in some games.

    Build 28000.2113
    Security 62 CVEs 4 critical
    Replaced by KB5089570 →
  • Windows 11 · 24H2, 25H2
    Windows 11 24H2 / 25H2 Windows 11 24H2 / 25H2 Security update
    KB5089549

    Critical DNS Client flaw patched; BitLocker startup risk reduced

    A critical DNS Client code-execution flaw is among the security fixes, and boot-file updates are less likely to trigger BitLocker recovery. Devices with little EFI partition space might fail installation.

    Builds 26100.8457 26200.8457
    Security 61 CVEs 4 critical
    Known issues 1 open
    Replaced by KB5089573 →
  • Windows 11 · 23H2
    Windows 11 23H2 Windows 11 23H2 Security update
    KB5087420

    Critical DNS Client flaw patched; BitLocker recovery prompt remains

    Critical vulnerabilities include a DNS Client remote code execution flaw. Some managed PCs might ask for a BitLocker recovery key after the first restart.

    Build 22631.7079
    Security 56 CVEs 5 critical
    Known issues 1 open
    Replaced by KB5093998 →
  • Windows 10 · 21H2, 22H2
    Windows 10 21H2 / 22H2 Windows 10 21H2 / 22H2 Security update
    KB5087544

    Secure Boot certificates begin expiring; Remote Desktop warning fixed

    Secure Boot certificates have started expiring in June 2026, which might affect secure booting on some devices if they are not updated in time; Microsoft recommends reviewing its preparation guidance. The update also fixes a Remote Desktop warning display issue.

    Builds 19044.7291 19045.7291
    Security 54 CVEs 3 critical
    Replaced by KB5094127 →
  • Windows 10 · 1809
    Windows 10 1809 Windows 10 1809 Security update Also for Windows Server
    KB5087538

    Secure Boot certificate coverage expands; sign-in errors fixed

    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.

    Build 17763.8755
    Security 52 CVEs 3 critical
    Replaced by KB5094123 →