Can I upgrade the Vertica Community Edition VM Linux?

You can run Vertica on the latest minor version listed in the supported versions shown in the documentation.
For Vertica 9.3.x it is CentOS 6.x and 7.x
see: https://www.vertica.com/docs/9.3.x/HTML/Content/Authoring/SupportedPlatforms/MCandServer.htm

Please note that you cannot perform an in-place upgrade of your current Vertica DB from CentOS 6.6–6.9 to CentOS 7.0/7.3/7.4/7.5/7.6.
For information on how to upgrade to CentOS 7.0/7.3/7.4/7.5/7.6 see:
https://www.vertica.com/docs/9.3.x/HTML/Content/Authoring/InstallationGuide/rhel7centos7migration.htm

@mosheg said:
You can run Vertica on the latest minor version listed in the supported versions shown in the documentation.
For Vertica 9.3.x it is CentOS 6.x and 7.x
see: https://www.vertica.com/docs/9.3.x/HTML/Content/Authoring/SupportedPlatforms/MCandServer.htm

Please note that you cannot perform an in-place upgrade of your current Vertica DB from CentOS 6.6–6.9 to CentOS 7.0/7.3/7.4/7.5/7.6.
For information on how to upgrade to CentOS 7.0/7.3/7.4/7.5/7.6 see:
https://www.vertica.com/docs/9.3.x/HTML/Content/Authoring/InstallationGuide/rhel7centos7migration.htm

Thanks @mosheg , glad that I asked before making decision. One more question: It seems that Vertica supports Python up to 3.4.3, but I tried to use pyodbc with Python 3.7+ with success. So this 3.4.3 is not a hard requirement? Thanks!

Python Version 3.3.4 is supported with Python Driver Module pyodbc 3.0.7
Other versions may also work, but the supported ones were tested.
If you will open a support case in the future, the support engineer might ask if the issue happens also with a supported version.