Vulnerability Discussion
In order to ensure that DNS resolver settings are respected, a DNS mode in Network Manager must be configured.
Check
Verify that RHEL 9 has a DNS mode configured in Network Manager.
$ NetworkManager --print-config
[main]
dns=none
If the dns key under main does not exist or is not set to "none" or "default", this is a finding.
Fix
Configure NetworkManager in RHEL 9 to use a DNS mode.
In "/etc/NetworkManager/NetworkManager.conf" add the following line in the "[main]" section:
dns = none
NetworkManager must be reloaded for the change to take effect.
$ sudo systemctl reload NetworkManager