DNS server freezes and doesn't respond to DNS requests in Windows Server 2012 R2

Applies to: Windows Server 2012 R2 DatacenterWindows Server 2012 R2 StandardWindows Server 2012 R2 Essentials

This article describes an issue in which a Domain Name System (DNS) server freezes and doesn't respond to DNS requests in Windows Server 2012 R2. A hotfix is available to fix this issue. Before you install this hotfix, see the Prerequisites section.


Assume that you're running Microsoft DNS Services on Windows Server 2012 R2-based computers in an Active Directory Forest. You notice that the DNS service on Windows Server 2012 R2-based DNS servers consumes increasing amounts of memory, and then memory leak occurs.

Additionally, the memory leaks by DNS may affect the performance of other components, services, and applications that are running on the same computer.

The Dnscmd cmdlet may show a signature that looks something like this:
Tagged Allocations:
Alloc = 8
Free = 7
InUse = 1
Mem = 160
UDP Packet
Alloc = 922979
Free = 513189
InUse = 409,790
Mem = 2,966,879,600
TCP Packet
Alloc = 2789088
Free = 2624289
InUse = 164799
Note If there're lots of UDP or TCP packages, you may hit the leak.


To fix this issue, we have released a hotfix for Windows Server 2012 R2.

Hotfix information

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

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that's described in this article. Apply this hotfix only to systems that are experiencing this specific problem.

If the hotfix is available for download, there's a "Hotfix Download Available" section at the top of this Knowledge Base article. If this section doesn't appear, submit a request to Microsoft Customer Service and Support to get the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that don't qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft website: Note The "Hotfix Download Available" form displays the languages for which the hotfix is available. If you don't see your language, it's because a hotfix isn't available for that language.


To apply this hotfix, install update 2919355 in Windows Server 2012 R2.

Registry information

To use the hotfix in this package, you don't have to make any changes to the registry.

Restart requirement

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

Hotfix replacement information

This hotfix doesn't replace a previously released hotfix.


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


See 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.