Vulnerability Discussion

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

Check

Note: If IPv6 is disabled on the system, this requirement is Not Applicable.

Verify that OL 9 ignores IPv6 ICMP redirect messages.

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

$ sysctl net.ipv6.conf.all.accept_redirects
net.ipv6.conf.all.accept_redirects = 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 OL 9 to ignore IPv6 ICMP redirect messages.

Add or edit the following line in a single system configuration file in the "/etc/sysctl.d/" directory:

net.ipv6.conf.all.accept_redirects = 0

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

$ sudo sysctl --system