RHEL 10 must not accept router advertisements on all Internet Protocol version 6 (IPv6) interfaces by default.

An illicit router advertisement message could result in a man-in-the-middle attack.

Satisfies: SRG-OS-000420-GPOS-00186, SRG-OS-000142-GPOS-00089

Note: If IPv6 is disabled on the system, this requirement is not applicable.

Verify RHEL 10 does not accept router advertisements on all IPv6 interfaces by default, unless the system is a router.

Check the value of the "net.ipv6.conf.default.accept_ra" variable with the following command:

$ sudo sysctl net.ipv6.conf.default.accept_ra net.ipv6.conf.default.accept_ra = 0

If "net.ipv6.conf.default.accept_ra" is not set to "0" or is missing, this is a finding.

Configure RHEL 10 to not accept router advertisements on all IPv6 interfaces by default, unless the system is a router.

Create a configuration file if it does not already exist:

$ sudo vi /etc/sysctl.d/ipv6_accept_ra.conf

Add the following line to the file:

net.ipv6.conf.default.accept_ra = 0

Reload settings from all system configuration files with the following command:

$ sudo sysctl --system