Title

RHEL 9 must not enable IPv4 packet forwarding unless the system is a router. (Cat II impact)

Discussion

Routing protocol daemons are typically used on routers to exchange network topology information with other routers. If this capability is used when not required, system network information may be unnecessarily transmitted across the network.

Check Content

Verify RHEL 9 is not performing IPv4 packet forwarding, unless the system is a router. Check that IPv4 forwarding is disabled using the following command: $ sudo sysctl net.ipv4.conf.all.forwarding net.ipv4.conf.all.forwarding = 0 If the IPv4 forwarding value is not "0" and is not documented with the information system security officer (ISSO) as an operational requirement, this is a finding. Check that the configuration files are present to enable this network parameter. $ sudo (/usr/lib/systemd/systemd-sysctl --cat-config; cat /etc/sysctl.conf) | egrep -v '^(#|$)' | grep net.ipv4.conf.all.forwarding | tail -1 net.ipv4.conf.all.forwarding = 0 If "net.ipv4.conf.all.forwarding" is not set to "0" and is not documented with the ISSO as an operational requirement or is missing, this is a finding.

Fix Text

Configure RHEL 9 to not allow IPv4 packet forwarding, unless the system is a router. Add or edit the following line in a single system configuration file, in the "/etc/sysctl.d/" directory: net.ipv4.conf.all.forwarding = 0 Load settings from all system configuration files with the following command: $ sudo sysctl --system

Additional Identifiers

Rule ID: SV-257970r943001_rule

Vulnerability ID: V-257970

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

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.