topic Re: High CPU usage by vmnat.exe after upgrade to VMware® Workstation 17 Pro version 17.5.0 build-225 in VMware Workstation Pro Discussions

High CPU usage by vmnat.exe after upgrade to VMware® Workstation 17 Pro version 17.5.0 build-2258379

Lippolt — Sat, 21 Oct 2023 01:16:48 GMT

I just upgraded to VMware® Workstation 17 Pro version 17.5.0 build-22583795. Since then my system has a high processor load due to the file vmnat.exe (version from 10.10.2023, digitally signed by VMware). One processor core is 100% utilized.

I did not find anything in this direction in the release notes. What can be done about this?

With best regards from Hannover Germany,
Peter Lippolt

Re: High CPU usage by vmnat.exe after upgrade to VMware® Workstation 17 Pro version 17.5.0 build-225

jen2 — Sat, 21 Oct 2023 10:22:29 GMT

It is a very aggressive bug I have already reported here https://communities.vmware.com/t5/Workstation-2023-Tech-Preview/BUG-VMware-NAT-Service-high-CPU-usage-build-22060606/m-p/2978665#M5

The only solution is to replace vmnat.exe in the C:\Windows\SysWOW64 with the old version 17.0.2. But you have to stop the service first (VMware NAT Service)

I will upload the file for anyone having this bug.

Re: High CPU usage by vmnat.exe after upgrade to VMware® Workstation 17 Pro version 17.5.0 build-225

louyo — Sat, 21 Oct 2023 10:31:22 GMT

This was reported during the trial:

https://communities.vmware.com/t5/Workstation-2023-Tech-Preview/BUG-VMware-NAT-Service-high-CPU-usage-build-22060606/td-p/2978665

His "fix" seems a little drastic. Hopefully, someone else has a better one.

If you have support contract, you might want to contact them.

Re: High CPU usage by vmnat.exe after upgrade to VMware® Workstation 17 Pro version 17.5.0 build-225

jen2 — Sat, 21 Oct 2023 10:43:36 GMT

That was me, and it was the same fix

Re: High CPU usage by vmnat.exe after upgrade to VMware® Workstation 17 Pro version 17.5.0 build-225

louyo — Sat, 21 Oct 2023 11:06:32 GMT

Sorry about that, I was typing while you were entering. Should have double checked.

Lou

Re: High CPU usage by vmnat.exe after upgrade to VMware® Workstation 17 Pro version 17.5.0 build-225

Maxvatar — Sat, 21 Oct 2023 12:29:47 GMT

Hi Peter,

same here. The only proper solution is to uninstall 17.5 and download "VMware-workstation-full-17.0.0-20800274.exe" from VM site ... it is still available there.

I wonder why VMWare release the 17.5 build when the high-cpu-usage bug of vmnat.exe is known from prerelease version, as Jen2 mentioned. It is rather weird in case of such software company as VMWare is.

Best regards

Tomas

Re: High CPU usage by vmnat.exe after upgrade to VMware® Workstation 17 Pro version 17.5.0 build-225

louyo — Sat, 21 Oct 2023 14:54:48 GMT

Voice of experience: The devs said fix it, the suits said ship it.

Re: High CPU usage by vmnat.exe after upgrade to VMware® Workstation 17 Pro version 17.5.0 build-225

merlingecko — Sat, 21 Oct 2023 15:38:20 GMT

same problem here

Re: High CPU usage by vmnat.exe after upgrade to VMware® Workstation 17 Pro version 17.5.0 build-225

seekay3309 — Sun, 22 Oct 2023 02:16:49 GMT

Same problem. I wish I knew about this bug beforehand. I'll try to revert now.

Re: High CPU usage by vmnat.exe after upgrade to VMware® Workstation 17 Pro version 17.5.0 build-225

jen2 — Sun, 22 Oct 2023 08:52:48 GMT

@Maxvatar wrote:
Hi Peter,
same here. The only proper solution is to uninstall 17.5 and download "VMware-workstation-full-17.0.0-20800274.exe" from VM site ... it is still available there.
I wonder why VMWare release the 17.5 build when the high-cpu-usage bug of vmnat.exe is known from prerelease version, as Jen2 mentioned. It is rather weird in case of such software company as VMWare is.
Best regards
Tomas

@seekay3309 wrote:
Same problem. I wish I knew about this bug beforehand. I'll try to revert now.

I would not recommend to revert unless you don't care of security! There are lots of CVE fixes.

The best way IMHO id you care about security is to replace only the vmnat.exe with old version I attached in post 2

Re: High CPU usage by vmnat.exe after upgrade to VMware® Workstation 17 Pro version 17.5.0 build-225

seekay3309 — Sun, 22 Oct 2023 15:52:08 GMT

Sigh. I already re-ran the 17.0 Installer, but it wouldn't downgrade 17.5 to 17.0. I un-installed 17.5 and re-installed 17.0. All settings (license keys, drive sharing, VMs) had to be put back. I also had to restore a Windows VM from a week-old backup so I lost a few minor updates/changes (but nothing major). Fortunately, I monitor my CPU utilization and background processes or I wouldn't have known.

The Installer I had this issue with is VMware-workstation-full-17.0.2-21581411.exe. Hopefully a new Installer with the fix gets posted soon so others don't have this issue too.

And yes. I am security conscious. That's why right off I didn't install a .exe file posted on a forum.

Re: High CPU usage by vmnat.exe after upgrade to VMware® Workstation 17 Pro version 17.5.0 build-225

jen2 — Sun, 22 Oct 2023 17:01:44 GMT

@seekay3309 wrote:
Sigh. I already re-ran the 17.0 Installer, but it wouldn't downgrade 17.5 to 17.0. I un-installed 17.5 and re-installed 17.0. All settings (license keys, drive sharing, VMs) had to be put back. I also had to restore a Windows VM from a week-old backup so I lost a few minor updates/changes (but nothing major). Fortunately, I monitor my CPU utilization and background processes or I wouldn't have known.
The Installer I had this issue with is VMware-workstation-full-17.0.2-21581411.exe. Hopefully a new Installer with the fix gets posted soon so others don't have this issue too.
And yes. I am security conscious. That's why right off I didn't install a .exe file posted on a forum.

It is the original file from VMWare 17.02 and it is signed by VMWare. The file is scanned by vmware before published, and you can check it using https://www.virustotal.com/gui/home/upload

Do you think I am so stupid to put a virus in the official VMWare forum? The file will be removed and I will be banned immediately

Re: High CPU usage by vmnat.exe after upgrade to VMware® Workstation 17 Pro version 17.5.0 build-225

Lippolt — Sun, 22 Oct 2023 22:08:29 GMT

The vmnat.exe posted by Enthusiast is code-signed by VMware. At least a strong sign for being OK.

Re: High CPU usage by vmnat.exe after upgrade to VMware® Workstation 17 Pro version 17.5.0 build-225

visentet — Wed, 25 Oct 2023 17:03:48 GMT

Many thanks, I was already thinking about a downgrade of entiero VMware.

Re: High CPU usage by vmnat.exe after upgrade to VMware® Workstation 17 Pro version 17.5.0 build-225

Julio_Imdg — Fri, 27 Oct 2023 04:15:50 GMT

Same problem.

Using vmnat.exe 17.0.2. did not help!

Re: High CPU usage by vmnat.exe after upgrade to VMware® Workstation 17 Pro version 17.5.0 build-225

jen2 — Fri, 27 Oct 2023 11:25:19 GMT

@Julio_Imdg wrote:
Same problem.
Using vmnat.exe 17.0.2. did not help!

Are you sure that you replaced the file in the C:\Windows\SysWOW64 folder?

Re: High CPU usage by vmnat.exe after upgrade to VMware® Workstation 17 Pro version 17.5.0 build-225

Lippolt — Fri, 27 Oct 2023 11:38:10 GMT

Hi Jen2,

I am sure I have modified the file in the following directory: C:\Windows\SysWOW64. I found the directory via Task Manager and the process with the high processor load. As you know, you can see the path to the executable under Details.
Replacing the file can only be done after successfully stopping the service in the Service Manager. Since I did this, I have no more problems. As soon as I copy the original file back from VMware Workstations pro 17.5, the problem reappears.

Greetings from Hanover, Germany,
Peter

Re: High CPU usage by vmnat.exe after upgrade to VMware® Workstation 17 Pro version 17.5.0 build-225

visentet — Fri, 27 Oct 2023 11:51:03 GMT

Hi Lippolt.

You don't have to copy the original, you have to leave the vmnat.exe from version 17.0.2. Start the service and work correctly.

Re: High CPU usage by vmnat.exe after upgrade to VMware® Workstation 17 Pro version 17.5.0 build-225

Julio_Imdg — Fri, 27 Oct 2023 21:55:20 GMT

Hi Jen2!

Sorry, I did a Mistake.
Before replacement, I found two copies of that file vmnat.exe. One located in C:\Program Files (x86)\VMware\VMware Workstation and the other in C:\Windows\SysWOW64 . I thought.. I replaced both. However I just have doublechecked. For some reason the syswow64 still had the 17.5 version. So, I replaced that file for the 17.0.2 version.
I have been monitoring cpu usage (two hours) using two WIndows 10 guest VM. No vmnat issues showed so far.

Thanks

Re: High CPU usage by vmnat.exe after upgrade to VMware® Workstation 17 Pro version 17.5.0 build-225

erobrich — Sat, 28 Oct 2023 18:35:06 GMT

I hit this problem as well. VMware NAT Service runs somewhere between 18 and 30% of my host's CPU all the time -- even when both guest and host are completely idle. Additionally, guests lost DNS through NAT service, and I had to add manual DNS servers to all guests. Host and guest are Win 11 22H2, fully patched. I'd really rather not downgrade. Hopefully 17.5.1 comes quickly and patches this?