RHEL 10 must not forward Internet Protocol version 6 (IPv6) source-routed packets by default.

Source-routed packets allow the source of the packet to suggest that routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures. This requirement applies only to the forwarding of source-routed traffic, such as when forwarding is enabled and the system is functioning as a router.

Accepting source-routed packets in the IPv6 protocol has few legitimate uses. It must be disabled unless it is absolutely required.

Satisfies: SRG-OS-000420-GPOS-00186, SRG-OS-000142-GPOS-00091

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

Verify RHEL 10 does not accept IPv6 source-routed packets by default.

Check the value of the "net.ipv6.conf.default.accept_source_route" variables with the following command:

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

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

Configure RHEL 10 to not accept IPv6 source-routed packets by default.

Create a configuration file if it does not already exist:

$ sudo vi /etc/sysctl.d/ipv6_accept_source_route.conf

Add the following line to the file:

net.ipv6.conf.default.accept_source_route = 0

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

$ sudo sysctl --system