Possible DNS Server memory leak

I have a Windows Server 2012 R2 physical server running AD DS, DNS roles. Very frequently DNS Server process starts consuming a lot of memory.

In Task Manager > Details > Analyze wait chain - I can see the following message:

"One or more threads of dns.exe are waiting to finish network I/O."

If I then run Process Explorer - I can see a bunch of threads:

Due to above problem - users experience name resolution issues.

Once the DNS Server service is restarted - the issue is gone for some time.

Is there any known fix for this?

UPD1:

Server has 8GB of RAM totally and 2 vCPUs.

DNS Server process is using 1.7GB of RAM and 40-60% CPU.

Number of DNS queries varies from 40 to 100 per second.

Here is the statistics for the last 2.5h:

Solution 1:

Sounds like this hotfix may help you https://support.microsoft.com/en-us/kb/3082532

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.

DNS hotfix has this prerequisite https://support.microsoft.com/en-us/kb/2919355