Title

The system must ignore IPv6 ICMP redirect messages. (Cat II impact)

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 Content

Verify the system is configured to ignore IPv6 ICMP redirect messages. # cat /proc/sys/net/ipv6/conf/all/accept_redirects If the /proc/sys/net/ipv6/conf/all/accept_redirects entry does not exist because of compliance with GEN007720, this is not a finding. If the returned value is not "0", this is a finding.

Fix Text

Configure the system to ignore IPv6 ICMP redirect messages. Edit "/etc/sysctl.conf" and add a settings for "net.ipv6.conf.default.accept_redirects=0" and "net.ipv6.conf.all.accept_redirects=0". Restart the system for the setting to take effect.

Additional Identifiers

Rule ID: SV-45990r2_rule

Vulnerability ID: V-22550

Group Title: GEN007860

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.