2018-08 Cumulative Update for Windows 10 Version 1803 for x64-based Systems (KB4343909)

Mar 9, 2005
Its super patch Tuesday again and MS has released KB4343909. I'm still in the process of downloading it right now so I cannot comment on it yet but here are the details.


August 14, 2018—KB4343909 (OS Build 17134.228)

Applies to: Windows 10, version 1803
Note This release also contains updates for Microsoft HoloLens (OS Build 17134.228) released August 14, 2018.
Improvements and fixes
This update includes quality improvements. No new operating system features are being introduced in this update. Key changes include:
  • Provides protections against a new speculative execution side-channel vulnerability known as L1 Terminal Fault (L1TF) that affects Intel® Core® processors and Intel® Xeon® processors (CVE-2018-3620 and CVE-2018-3646). Make sure previous OS protections against Spectre Variant 2 and Meltdown vulnerabilities are enabled using the registry settings outlined in the Windows Client and Windows Server guidance KB articles. (These registry settings are enabled by default for Windows Client OS editions, but disabled by default for Windows Server OS editions.)
  • Addresses an issue that causes high CPU usage that results in performance degradation on some systems with Family 15h and 16h AMD processors. This issue occurs after installing the June 2018 or July 2018 Windows updates from Microsoft and the AMD microcode updates that address Spectre Variant 2 (CVE-2017-5715 – Branch Target Injection).
  • Addresses an issue that prevents apps from receiving mesh updates after resuming. This issue occurs for apps that use Spatial Mapping mesh data and participate in the Sleep or Resume cycle.
  • Ensures that Internet Explorer and Microsoft Edge support the preload="none" tag.
  • Addresses an issue that prevents some applications running on HoloLens, such as Remote Assistance, from authenticating after upgrading from Windows 10, version 1607, to Windows 10, version 1803.
  • Addresses an issue that significantly reduced battery life after upgrading to Windows 10, version 1803.
  • Addresses an issue that causes Device Guard to block some ieframe.dll class IDs after installing the May 2018 Cumulative Update.
  • Addresses a vulnerability related to the Export-Modulemember() function when used with a wildcard (*) and a dot-sourcing script. After installing this update, existing modules on devices that have Device Guard enabled will intentionally fail. The exception error is “This module uses the dot-source operator while exporting functions using wildcard characters, and this is disallowed when the system is under application verification enforcement.” For more information, see https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2018-8200 and https://aka.ms/PSModuleFunctionExport.
  • Security updates to Windows Server.
If you installed earlier updates, only the new fixes in this package will be downloaded and installed on your device.
For more information about the resolved security vulnerabilities, see the Security Update Guide.
Known issues in this update
Symptom Workaround
After you install any of the July 2018 .NET Framework Security Updates, a COM component fails to load because of “access denied,” “class not registered,” or “internal failure occurred for unknown reasons” errors. The most common failure signature is the following:
Exception type: System.UnauthorizedAccessException
Message: Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED))

For more information, see KB4345913.
Microsoft is working on a resolution and will provide an update in an upcoming release.
How to get this update
This update will be downloaded and installed automatically from Windows Update. To get the standalone package for this update, go to the Microsoft Update Catalog website.
File information
For a list of the files that are provided in this update, download the file information for cumulative update 4343909.
Last Updated: Aug 14, 2018
Aug 25, 2001
The MRT seems to have deleted some of my NH miner software, even though I have a directory exception for it under Windows Defender in Win10.


Diamond Member
Oct 17, 1999
MRT is an on demand scanner that is probably not reading exclusions for defender. I set the registry key to disable MRT on every computer I touch or deploy because in all these years all it has caused is windows update hangups and delays just to perhaps improve one computer that had a compromised Dell certificate in its certificate store.


Diamond Member
Oct 9, 1999