Rule version OL09-00-006041 · STIG v1 · 2026-08-21
An illicit ICMP redirect message could result in a man-in-the-middle attack.
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.
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