Vulnerability Discussion

ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages modify the host's route table and are unauthenticated. An illicit ICMP redirect message could result in a man-in-the-middle attack.

Check

Verify the SUSE operating system ignores IPv4 ICMP redirect messages.

Check the value of the "accept_redirects" variables with the following command:

# sysctl net.ipv4.conf.default.accept_redirects
net.ipv4.conf.default.accept_redirects = 0

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

Fix

Configure the SUSE operating system ignores IPv4 ICMP redirect messages by adding the following line to "/etc/sysctl.conf" (or modify the line to have the required value):

net.ipv4.conf.default.accept_redirects = 0

Run the following command to apply this value:

# sysctl --system