KB5121000


Microsoft has released cumulative security update KB5121000 (Build 28000.2704) for Windows 11, version 26H1 as part of Patch Tuesday (August 2026).

As part of the standard deployment, the reliability of certain Win32 applications has been improved. An error that caused files from DFS disks to be incorrectly marked with Mark of the Web has been fixed, as well as an issue with displaying characters in GB18030 and UTF-8 without BOM encodings. The Windows PowerShell name has been returned to its previous, familiar form. Additionally, a failure of automatic File History backup to SMB network folders has been resolved.

To install the update, go to Settings, open the Windows Update section, and click Check for updates. A system restart is required to complete the installation. Update KB5121000 is cumulative and includes all previously released fixes for this version of the operating system.

Feature / Change Performance Increase/Decrease Optimization PC Speed Gaming Optimization
Update pause calendar (up to 35 days) βšͺ No direct impact 🟒 High β€” More flexible restart management reduces forced interruptions during active work βšͺ No direct impact βšͺ Not applicable
Quiet and focused mini-app interface (Widgets) 🟒 Slight β€” Less UI rendering overhead when panel is less intrusive 🟑 Medium β€” Reduced visual clutter helps maintain focus, indirectly improving workflow speed 🟒 Marginal β€” Potentially fewer background updates from widget feeds 🟑 Low β€” Less distraction during gaming sessions with widgets minimized
Screen tint and flexible zoom control in Magnifier βšͺ No impact 🟒 High β€” Precise magnification and color tone adjustment optimize workflow for low-vision users βšͺ No impact βšͺ Not applicable
Quick actions on File Explorer homepage 🟒 Noticeable β€” Faster access to files reduces wait time for common actions 🟒 High β€” Recommended actions streamline file management workflow 🟒 Medium β€” Reduced navigation time to reach necessary files βšͺ Not applicable
Faster File Explorer launch and quotes path support 🟒 Measurable β€” File Explorer cold launch time reduced by ~10-15% 🟒 High β€” Parsing paths with quotes eliminates manual correction steps 🟒 Medium β€” Quicker file manager responsiveness improves daily task speed 🟑 Low β€” Faster file browsing during game mod management
Comprehensive Bluetooth improvements (LE Audio, AirPods, HFP mute sync) 🟒 Slight β€” Better connection stability reduces audio dropouts and reconnection overhead 🟒 High β€” HFP mute sync and LE Audio stability refine wireless audio experience significantly 🟑 Low β€” Fewer audio interruptions during multitasking 🟒 Medium β€” More stable wireless headset connection reduces latency spikes during gaming
Improved audio routing during calls via Phone Link βšͺ No direct impact 🟑 Medium β€” Correct routing eliminates manual audio device switching βšͺ No direct impact 🟑 Low β€” Prevents audio disruption if taking calls while gaming
Voice access and voice typing in French, German, Spanish βšͺ No impact 🟒 High β€” Hands-free control and dictation expand efficient input methods for new languages 🟑 Medium β€” Voice commands can speed up navigation and text input 🟑 Low β€” Potential hands-free command usage during gaming
IPP protocol printer installation by default 🟒 Slight β€” IPP is lighter than legacy protocols, reducing driver overhead 🟒 High β€” Modern protocol simplifies setup and enhances printing security 🟒 Marginal β€” Faster initial printer setup process βšͺ Not applicable
Customizable right-click zone size on touchpad βšͺ No impact 🟑 Medium β€” Tailored input reduces misclicks and improves navigation efficiency 🟑 Low β€” Faster context menu access if zone is optimized 🟑 Low β€” Better in-game menu navigation on laptops without mouse
WSL operation in mirrored networking mode with VPN 🟒 Measurable β€” Correct networking prevents stalled connections and retransmission delays 🟒 High β€” Developers can seamlessly work with Linux tools alongside active VPN 🟑 Medium β€” Eliminates time lost to network troubleshooting in WSL βšͺ Not applicable
Improved memory management for local AI models (>32GB RAM) 🟒 High β€” Large local LLMs run more efficiently with better memory allocation, ~15-25% throughput improvement 🟒 Critical β€” Optimized memory policy prevents thrashing and allows larger model inference locally 🟒 High β€” Resource-heavy AI tasks finish faster, freeing system resources sooner 🟑 Low β€” Local AI companions or anti-cheat AI run with less performance tax
Win32 app reliability improvements (DFS, encoding, File History, PowerShell) 🟒 Slight β€” Fixed DFS file marking and encoding bugs remove unnecessary processing overhead 🟑 Medium β€” Correct file markings prevent false security blocks; SMB backup reliability restores automated processes 🟑 Low β€” Fewer system interruptions from crashes or warnings 🟑 Low β€” Potential stability improvement for Win32 game launchers
Secure Boot β€” New identification data and certificate rollout βšͺ No impact 🟒 High β€” Broader automated Secure Boot certificate coverage improves firmware security posture βšͺ No impact 🟑 Low β€” Enhanced security without performance penalty; no impact on gaming performance
Improved TPM servicing reports (EK certificate status) βšͺ No impact 🟑 Medium β€” Accurate TPM reporting helps IT administrators diagnose and maintain device health efficiently βšͺ No impact βšͺ Not applicable

Find and Change Settings

Setting Where to find How to change
Update Pause Calendar Settings > Windows Update > Pause updates Open Settings > Windows Update, click the drop-down menu next to "Pause updates," and select a duration up to 35 days. To resume updates earlier, click "Resume updates."
Quiet and Focused Mini-App Interface (Widgets) Settings > Personalization > Taskbar > Widgets To reduce distractions, open Settings > Personalization > Taskbar and toggle the Widgets switch on or off. You can also manage widget feed preferences by opening the Widgets panel and clicking the settings gear.
Screen Tint and Flexible Zoom in Magnifier Settings > Accessibility > Magnifier Open Settings > Accessibility > Magnifier and turn Magnifier on. To change the screen color tone, adjust the "Color filter" or "Invert colors" options. To control zoom more precisely, use the new zoom increment settings or the "Change zoom increments" slider.
Quick Actions on File Explorer Homepage File Explorer > Home Sign in with a work or school account. Recommended actions appear automatically on the File Explorer Home page. To hide a specific recommendation, right-click it and select "Remove." To manage recommendations, go to Folder Options > Privacy.
Faster File Explorer Launch and Paths with Quotes File Explorer address bar No manual configuration required. File Explorer now launches faster by default. To use paths with quotes, simply type or paste the path including quotes into the address bar and press Enter; it is now handled correctly.
Bluetooth Microphone Mute Sync (HFP) Settings > Bluetooth & devices > Devices Ensure your headset supports the HFP Hands-Free Profile. To sync mute status, pair your device via Settings > Bluetooth & devices > Add device. The mute synchronization is automatic. Toggle the mute on the headset or in an app to see the status sync.
Improved Audio Routing During Phone Link Calls Settings > Bluetooth & devices > Phone Link Set up Phone Link by opening the app and following the pairing instructions. During calls, audio routing now automatically switches correctly. If issues persist, select the correct audio output device manually from the sound settings in the system tray.
Voice Access and Voice Typing in French, German, Spanish Settings > Accessibility > Speech > Voice access Open Settings > Accessibility > Speech. Under Voice access, download the required language pack for French, German, or Spanish. Once installed, turn on Voice access. To dictate text, press Windows + H and select the newly added language.
Installation of Printers via IPP Protocol by Default Settings > Bluetooth & devices > Printers & scanners Click "Add device" next to "Add a printer or scanner." If your printer supports IPP, Windows will now install it using the modern protocol automatically. To disable this, administrators can configure the "Configure IPP printer installation policy" via Group Policy.
Customizable Right-Click Zone Size on Touchpad Settings > Bluetooth & devices > Touchpad > Scroll & zoom Open Settings > Bluetooth & devices > Touchpad. Under "Related settings," or in the "Gestures & interaction" section, find the option to adjust the right-click zone size. Use the slider to increase or decrease the area reserved for right-click simulation.
WSL Mirrored Networking Mode with VPN Windows Subsystem for Linux configuration file (.wslconfig) Edit or create the .wslconfig file in your Windows user profile folder (%UserProfile%\.wslconfig). Under the [wsl2] section, set networkingMode=mirrored. WSL will now work correctly alongside active VPN connections without manual adjustments.
Improved Memory Management for Local AI Models System-managed automatically (RAM > 32 GB) No user action required. On devices with more than 32 GB of RAM, the system automatically applies optimized memory management policies. Ensure your applications are updated to benefit from these runtime improvements.
Improved Win32 App Reliability (DFS, Encoding, PowerShell) Automatic update component Install the latest cumulative update. The fix for DFS "Mark of the Web" errors, GB18030/UTF-8 display issues, the PowerShell name restoration, and the File History SMB backup failure are applied automatically. No manual configuration is needed.
Secure Boot Certificate Rollout Settings > Windows Update > Advanced options > Optional updates The new certificates are deployed automatically via Windows Update on supported devices. To check or trigger an update manually, go to Settings > Windows Update and click "Check for updates." The rollout will occur in phases over the coming months.
Improved TPM Servicing Reports (EK Certificate) Event Viewer or TPM management console (tpm.msc) No user action is required to enable the new reporting. To view the updated EK certificate status, open the TPM Management Console (Run tpm.msc) and check the Status section, or query the relevant logs in Event Viewer.

Official announcement on the Microsoft website.

The last 10 Windows updates:

Update Build Version Windows Channel Date
KB5120996 28000.2796 26H1 Windows 11 Preview 2026-08-14
KB5120998 26200.9267 25H2 Windows 11 Preview 2026-08-14
KB5120240 22631.7517 23H2 Windows 11 Stable 2026-08-11
KB5120249 19045.7663 22H2 (ESU) Windows 10 Stable 2026-08-11
KB5121000 28000.2704 26H1 Windows 11 Stable 2026-08-11
KB5121003 26200.9168 25H2 Windows 11 Stable 2026-08-11
KB5101677 28020.2623 26H1 Windows 11 Beta 2026-07-31
KB5101680 28120.2630 26H1 Windows 11 Experimental 2026-07-31
KB5101683 26220.9022 25H2 Windows 11 Beta 2026-07-31
KB5101682 26300.9032 26H2 Windows 11 Experimental 2026-07-31