Vulnerability Discussion

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.

Check

Verify RHEL 8 does not accept IPv4 source-routed packets.

Note: If IPv4 is disabled on the system, this requirement is Not Applicable.

Check the value of the accept source route variable with the following command:

$ sudo sysctl net.ipv4.conf.all.accept_source_route

net.ipv4.conf.all.accept_source_route = 0

If the returned line does not have a value of "0", a line is not returned, or the line is commented out, this is a finding.

Fix

Configure RHEL 8 to not forward IPv4 source-routed packets with the following command:

$ sudo sysctl -w net.ipv4.conf.all.accept_source_route=0

If "0" is not the system's all value then add or update the following line in the appropriate file under "/etc/sysctl.d":

net.ipv4.conf.all.accept_source_route=0