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V-22416

CAT II (Medium)

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

Rule ID

SV-45726r1_rule

STIG

SUSE Linux Enterprise Server v11 for System z Security Technical Implementation Guide

Version

V1R12

CCIs

CCI-001503 CCI-001551

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 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

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