RHEL 8 must ignore IPv4 Internet Control Message Protocol (ICMP) redirect messages.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-244553	RHEL-08-040279	SV-244553r743908_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 8 Security Technical Implementation Guide	2021-06-14

Details

Check Text ( C-47828r743906_chk )
Verify RHEL 8 ignores IPv4 ICMP redirect messages. Note: If IPv4 is disabled on the system, this requirement is Not Applicable. Check the value of the "accept_redirects" variables with the following command: $ sudo sysctl net.ipv4.conf.all.accept_redirects net.ipv4.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.

Check Text ( C-47828r743906_chk )

Verify RHEL 8 ignores IPv4 ICMP redirect messages.

Note: If IPv4 is disabled on the system, this requirement is Not Applicable.

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

$ sudo sysctl net.ipv4.conf.all.accept_redirects

net.ipv4.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.

Fix Text (F-47785r743907_fix)
Configure RHEL 8 to ignore IPv4 ICMP redirect messages with the following command: $ sudo sysctl -w net.ipv4.conf.all.accept_redirects=0 If "0" is not the system's default value then add or update the following line in the appropriate file under "/etc/sysctl.d": net.ipv4.conf.all.accept_redirects = 0