Failed to start native messaging host on Windows, "COMSPEC is not set"

Question

I have a chrome extension that communicates with a native messaging host to get some data.

The issue is, when I launch the Chrome browser via the shortcut or via the pinned shortcut in the taskbar, the extension is not able to connect to the host. I always get the error:

Failed to start native messaging host.

However, if I launch the chrome.exe via command prompt, everything works fine.

Things I tried with no success:

• The taskbar shortcut has no extra flags. The target field has the following value: "C:\Program Files(x86)\Google\Chrome\Application\chrome.exe"
• I tried with the registry under HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Google\Chrome\NativeMessagingHosts\com.company.extension
• I tried with the registry under HKEY_LOCAL_MACHINE\SOFTWARE\Google\Chrome\NativeMessagingHosts\com.company.extension
• I tried with the registry entry under HKEY_CURRENT_USER\Software\Google\Chrome\NativeMessagingHosts\com.company.extension
• Tried launching the chrome.exe as administrator from the file explorer.

Update:

I added the flag --enable-logging --v=1 to the shortcut to enable logging and when I launch it I get the following output in the console:

[11036:4160:0302/113902.866:ERROR:native_process_launcher_win.cc(140)] COMSPEC is not set
[11036:11856:0302/113902.882:ERROR:native_process_launcher_win.cc(140)] COMSPEC is not set

Update

Upon investigating the chrome.exe process via Process Monitor, I found that there is no COMSPEC environment variable available to it when it is spawned via explorer.

Is there anything else that I can try or something that I am missing here?

Answer 1

As mentioned in the log, Chrome stumbles to start an external process, since COMSPEC, an environment variable pointing normally to cmd, is unset:

[11036:4160:0302/113902.866:ERROR:native_process_launcher_win.cc(140)] COMSPEC is not set

The behavior is different for launching Chrome from cmd itself, since it sets the variable for itself (ans spawned processes).

This can be confirmed by inspecting the Chrome process with Process Explorer.

One can run rundll32 sysdm.cpl,EditEnvironmentVariables as admin (e.g. from admin command line) to open the environment variable settings.
Alternatively, the dialog can be navigated to from Control Panel > System and Security > System > Advanced system settings > Advanced > Environment Variables...

ComSpec is usually set in System variables to

C:\WINDOWS\system32\cmd.exe

Adjust as necessary for your system install. For this setting to apply, you need to log out and log back in, or better yet restart the system.