The system must ignore IPv4 Internet Control Message Protocol (ICMP) redirect messages.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-22416	GEN003609	SV-45726r1_rule		Medium

Description
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.

STIG	Date
SUSE Linux Enterprise Server v11 for System z Security Technical Implementation Guide	2018-09-19

Details

Check Text ( C-43093r1_chk )
Verify the system does not accept IPv4 ICMP redirect messages. # grep [01] /proc/sys/net/ipv4/conf/*/accept_redirects|egrep "default|all" If all of the resulting lines do not end with "0", this is a finding.

Fix Text (F-39124r1_fix)
Configure the system to not accept IPv4 ICMP redirect messages. Edit /etc/sysctl.conf and add a setting for "net.ipv4.conf.all.accept_redirects=0" and "net.ipv4.conf.default.accept_redirects=0". # sysctl -p