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The system must ignore Internet Protocol version 4 (IPv4) Internet Control Message Protocol (ICMP) redirect messages.


Overview

Finding ID Version Rule ID IA Controls Severity
V-73175 RHEL-07-040641 SV-87827r3_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
Red Hat Enterprise Linux 7 Security Technical Implementation Guide 2017-12-14

Details

Check Text ( C-73299r2_chk )
Verify the system ignores IPv4 ICMP redirect messages.

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

# /sbin/sysctl -a | grep 'net.ipv4.conf.all.accept_redirects'

net.ipv4.conf.all.accept_redirects=0

If the returned line does not have a value of "0", or a line is not returned, this is a finding.
Fix Text (F-79621r2_fix)
Set the system to ignore IPv4 ICMP redirect messages by adding the following line to "/etc/sysctl.conf" (or modify the line to have the required value):

net.ipv4.conf.all.accept_redirects = 0