STIGQter: STIG Summary: Cloud Linux AlmaLinux OS 9 Security Technical Implementation Guide Version: 1 Release: 7 Benchmark Date: 01 Jul 2026:

AlmaLinux OS 9 must ignore Internet Control Message Protocol (ICMP) redirect messages.

DISA Rule

SV-269244r1050126_rule

Vulnerability Number

V-269244

Group Title

SRG-OS-000480-GPOS-00227

Rule Version

ALMA-09-018610

Severity

CAT II

CCI(s)

CCI-000366 - Implement the security configuration settings.

Weight

Fix Recommendation

Configure AlmaLinux OS 9 to ignore ICMP redirect messages.

Create a numbered *.conf file in /etc/sysctl.d/ with the following content:

net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.default.accept_redirects = 0
net.ipv4.conf.lo.accept_redirects = 0
net.ipv6.conf.all.accept_redirects = 0
net.ipv6.conf.default.accept_redirects = 0
net.ipv6.conf.lo.accept_redirects = 0

The system configuration files need to be reloaded for the changes to take effect. To reload the contents of the files, run the following command:

$ sysctl –system

Check Contents

Verify AlmaLinux OS 9 will not accept ICMP redirect messages.

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

$ sysctl -a | grep accept_redirects

net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.default.accept_redirects = 0
net.ipv4.conf.enp1s0.accept_redirects = 0
net.ipv4.conf.lo.accept_redirects = 0
net.ipv6.conf.all.accept_redirects = 0
net.ipv6.conf.default.accept_redirects = 0
net.ipv6.conf.enp1s0.accept_redirects = 0
net.ipv6.conf.lo.accept_redirects = 0

If the returned lines do not all have a value of "0", this is a finding.

Vulnerability Number

V-269244

Documentable

False

Rule Version

ALMA-09-018610

Severity Override Guidance

Check Content Reference

Target Key

5664