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V-281346

CAT II (Medium)

RHEL 10 must prevent Internet Protocol version 4 (IPv4) Internet Control Message Protocol (ICMP) redirect messages from being accepted.

Rule ID

SV-281346r1197251_rule

STIG

Red Hat Enterprise Linux 10 Security Technical Implementation Guide

Version

V1R1

CCIs

CCI-002385 CCI-001101

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. This feature of the IPv4 protocol has few legitimate uses. It must be disabled unless absolutely required. Satisfies: SRG-OS-000420-GPOS-00186, SRG-OS-000142-GPOS-00077

Check Content

Verify RHEL 10 will not accept IPv4 ICMP redirect messages.

Check the value of the default "net.ipv4.conf.default.accept_redirects" variable with the following command:

$ sudo sysctl net.ipv4.conf.default.accept_redirects
net.ipv4.conf.default.accept_redirects = 0

If "net.ipv4.conf.default.accept_redirects" is not set to "0" or is missing, this is a finding.

Fix Text

Configure RHEL 10 to prevent IPv4 ICMP redirect messages from being accepted.

Create a configuration file if it does not already exist:

$ sudo vi /etc/sysctl.d/99-ipv4_accept_redirects.conf

Add the following line to the file:

net.ipv4.conf.default.accept_redirects = 0

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

$ sudo sysctl --system