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 use reverse path filtering on all IP interfaces.

DISA Rule

SV-269255r1050137_rule

Vulnerability Number

V-269255

Group Title

SRG-OS-000480-GPOS-00227

Rule Version

ALMA-09-019820

Severity

CAT II

CCI(s)

• CCI-000366 - Implement the security configuration settings.

Weight

10

Fix Recommendation

Configure AlmaLinux OS 9 to use reverse path filtering on all IP interfaces.

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

net.ipv4.conf.all.rp_filter = 1
net.ipv4.conf.default.rp_filter = 1
net.ipv4.conf.lo.rp_filter = 1

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 uses reverse path filtering on all IP interfaces with the following command:

$ sysctl -a | grep -E '\.rp_filter'

net.ipv4.conf.all.rp_filter = 0
net.ipv4.conf.default.rp_filter = 1
net.ipv4.conf.enp1s0.rp_filter = 1
net.ipv4.conf.lo.rp_filter = 1

If the returned lines do not all have a value of "1", this is a finding.

Vulnerability Number

V-269255

Documentable

False

Rule Version

ALMA-09-019820

Severity Override Guidance

Verify AlmaLinux OS 9 uses reverse path filtering on all IP interfaces with the following command:

$ sysctl -a | grep -E '\.rp_filter'

net.ipv4.conf.all.rp_filter = 0
net.ipv4.conf.default.rp_filter = 1
net.ipv4.conf.enp1s0.rp_filter = 1
net.ipv4.conf.lo.rp_filter = 1

If the returned lines do not all have a value of "1", this is a finding.

Check Content Reference

M

Target Key

5664