← Back to Oracle Linux 9 Security Technical Implementation Guide

V-271875

CAT II (Medium)

OL 9 must not send Internet Control Message Protocol (ICMP) redirects.

Rule ID

SV-271875r1092337_rule

STIG

Oracle Linux 9 Security Technical Implementation Guide

Version

V1R5

CCIs

CCI-000366

Discussion

ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages contain information from the system's route table possibly revealing portions of the network topology. The ability to send ICMP redirects is only appropriate for systems acting as routers.

Check Content

Verify that OL 9 does not IPv4 ICMP redirect messages.

Check the value of the "all send_redirects" variables with the following command:

$ sysctl net.ipv4.conf.all.send_redirects
net.ipv4.conf.all.send_redirects = 0

If "net.ipv4.conf.all.send_redirects" is not set to "0" and is not documented with the information system security officer (ISSO) as an operational requirement or is missing, this is a finding.

Fix Text

Configure OL 9 to not allow interfaces to perform IPv4 ICMP redirects.

Add or edit the following line in a single system configuration file in the "/etc/sysctl.d/" directory:

net.ipv4.conf.all.send_redirects = 0

Load settings from all system configuration files with the following command:

$ sudo sysctl --system