RHEL 10 must ignore IPv6 Internet Control Message Protocol (ICMP) redirect messages.

An illicit ICMP redirect message could result in a man-in-the-middle attack.

Satisfies: SRG-OS-000420-GPOS-00186, SRG-OS-000142-GPOS-00086

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

Verify RHEL 10 ignores IPv6 ICMP redirect messages.

Check the value of the "net.ipv6.conf.all.accept_redirects" variable with the following command:

$ sysctl net.ipv6.conf.all.accept_redirects net.ipv6.conf.all.accept_redirects = 0

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

Configure RHEL 10 to ignore Internet Protocol version 6 (IPv6) ICMP redirect messages.

Create a configuration file if it does not already exist:

$ sudo vi /etc/sysctl.d/ipv6_accept_redirects.conf

Add the following line to the file:

net.ipv6.conf.all.accept_redirects = 0

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

$ sudo sysctl --system