Title

RHEL 9 must configure a DNS processing mode in Network Manager. (Cat II impact)

Discussion

To ensure that DNS resolver settings are respected, a DNS mode in Network Manager must be configured. The following are common DNS values in NetworkManager.conf [main]: - default: NetworkManager will update /etc/resolv.conf to reflect the nameservers provided by currently active connections. - none: NetworkManager will not modify /etc/resolv.conf. Used when DNS is managed manually or by another service. - systemd-resolved: Uses systemd-resolved to manage DNS. - dnsmasq: Enables the internal dnsmasq plugin.

Check Content

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 "default", "none", or "systemd-resolved", this is a finding. Note: If RHEL 9 is configured to use a DNS resolver other than Network Manager, the configuration must be documented and approved by the information system security officer (ISSO).

Fix Text

Configure NetworkManager in RHEL 9 to use a DNS mode. In "/etc/NetworkManager/NetworkManager.conf", add the following line in the "[main]" section: dns = <dns processing mode> Where <dns processing mode> is default, none, or systemd-resolved. NetworkManager must be reloaded for the change to take effect. $ sudo systemctl reload NetworkManager

Additional Identifiers

Rule ID: SV-257949r1134947_rule

Vulnerability ID: V-257949

Group Title: SRG-OS-000480-GPOS-00227

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