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 IPv4/IPv6 forwarding is enabled and the system is functioning as a router.

Check

Verify the SUSE operating system does not accept IPv4 source-routed packets.

Check the value of the IPv4 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 network parameter "ipv4.conf.all.accept_source_route" is not equal to "0" or nothing is returned, this is a finding.

Fix

Configure the SUSE operating system to disable IPv4 source routing by running the following command as an administrator:

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

If "0" is not the system's default value, add or update the following line in "/etc/sysctl.d/99-stig.conf":

> sudo sh -c 'echo "net.ipv4.conf.all.accept_source_route=0" >> /etc/sysctl.d/99-stig.conf'

> sudo sysctl --system