LSASS deadlocks cause Windows Server 2012 R2 or Windows Server 2012 not to respond

Windows Server 2012 R2 DatacenterWindows Server 2012 R2 StandardWindows Server 2012 R2 Essentials

This article describes an issue that occurs when Local Security Authority Subsystem Service (LSASS) deadlocks on Windows Server 2012 R2 or Windows Server 2012. You can fix this issue by using the update in this article. Before you install this update, see the Prerequisites section.


LSASS.exe may deadlock because of maxed out shared NT Thread Pool threads. This causes the server to stop responding to login requests from Exchange email clients such as Outlook, ActiveSync, and Outlook Web App as well as Remote Desktop connections, remote administrative commands through PowerShell, and local console logins.

How to get this update

You can get this update by using one of the following methods. We have released an update through Windows Update and Microsoft Update Catalog. Even though this issue is observed only in Windows Server 2012 R2 or Windows Server 2012, the update also applies to Windows 8.1, Windows RT 8.1, and Windows Embedded 8.

Important If you install a language pack after you install this update, you must reinstall this update. Therefore, we recommend that you install any language packs that you need before you install this update. For more information, see Add language packs to Windows.

Method 1: Windows Update

This update is provided as a Recommended update on Windows Update. For more information on how to run Windows Update, see How to get an update through Windows Update.

Method 2: Microsoft Update Catalog

To get the stand-alone package for this update, go to the Microsoft Update Catalog website.

Note You must be running Microsoft Internet Explorer 6.0 or later.

Update detail information


To apply this update in Windows 8.1 or Windows Server 2012 R2, you must have April 2014 update rollup for Windows RT 8.1, Windows 8.1, and Windows Server 2012 R2 (2919355) installed.

Registry information

To apply this update, you don't have to make any changes to the registry.

Restart requirement

You may have to restart the computer after you apply this update.

Update replacement information

This update doesn't replace a previously released update.


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.


This issue occurs because of flood of delete logon session requests that causes the thread pool to max out if there is a heavy load on the system.


Learn about the terminology that Microsoft uses to describe software updates.

File Information

The English (United States) version of this software update installs files that have the attributes that are listed in the following tables.