TOSS 5 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.

Verify TOSS 5 does not accept router advertisements on all IPv6 interfaces by default, unless the system is a router.

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

Determine if router advertisements are not accepted by default by using the following command:

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

net.ipv6.conf.default.accept_ra = 0

If the "accept_ra" value is not "0" and is not documented with the information system security officer (ISSO) as an operational requirement, this is a finding.

Configure TOSS 5 to not accept router advertisements on all IPv6 interfaces by default 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.ipv6.conf.default.accept_ra = 0

Load settings from all system configuration files using the following command:

$ sudo sysctl --system