STIGQter: STIG Summary: Red Hat Enterprise Linux 9 Security Technical Implementation Guide Version: 2 Release: 9 Benchmark Date: 01 Jul 2026:

The RHEL 9 firewall must employ a deny-all, allow-by-exception policy for allowing connections to other systems.

DISA Rule

SV-257937r1106310_rule

Vulnerability Number

V-257937

Group Title

SRG-OS-000480-GPOS-00227

Rule Version

RHEL-09-251020

Severity

CAT II

CCI(s)

• CCI-000366 - Implement the security configuration settings.

Weight

10

Fix Recommendation

Configure the "firewalld" daemon to employ a deny-all, allow-by-exception policy with the following commands:

Start by adding the exceptions that are required for mission functionality to the "drop" zone. If SSH access on port 22 is needed, for example, run the following: "sudo firewall-cmd --permanent --add-service=ssh --zone=drop"

Reload the firewall rules to update the runtime configuration from the "--permanent" changes made above:
$ sudo firewall-cmd --reload

Set the default zone to the drop zone:
$ sudo firewall-cmd --set-default-zone=drop
Note: This is a runtime and permanent change.

Add any interfaces to the newly modified "drop" zone:
$ sudo firewall-cmd --permanent --zone=drop --change-interface=ens192

Reload the firewall rules for changes to take effect:
$ sudo firewall-cmd --reload

Check Contents

Verify the RHEL 9 firewalld is configured to employ a deny-all, allow-by-exception policy for allowing connections to other systems with the following commands:

Ensure firewalld is running:
$ sudo firewall-cmd --state
running

Identify active zones:
$ sudo firewall-cmd --get-active-zones
drop
interfaces: ens192

Check what rules are applied in that zone:
$ sudo firewall-cmd --list-all --zone=$(firewall-cmd --get-default-zone)
drop (active)
target: DROP
icmp-block-inversion: no
interfaces: ens192
sources:
services: ssh
ports:
protocols:
forward: yes
masquerade: no
forward-ports:
source-ports:
icmp-blocks:
rich rules:

If no zones are active on the RHEL 9 interfaces or if runtime and permanent targets are set to a different option other than "DROP", this is a finding.

Vulnerability Number

V-257937

Documentable

False

Rule Version

RHEL-09-251020

Severity Override Guidance

Verify the RHEL 9 firewalld is configured to employ a deny-all, allow-by-exception policy for allowing connections to other systems with the following commands:

Ensure firewalld is running:
$ sudo firewall-cmd --state
running

Identify active zones:
$ sudo firewall-cmd --get-active-zones
drop
interfaces: ens192

Check what rules are applied in that zone:
$ sudo firewall-cmd --list-all --zone=$(firewall-cmd --get-default-zone)
drop (active)
target: DROP
icmp-block-inversion: no
interfaces: ens192
sources:
services: ssh
ports:
protocols:
forward: yes
masquerade: no
forward-ports:
source-ports:
icmp-blocks:
rich rules:

If no zones are active on the RHEL 9 interfaces or if runtime and permanent targets are set to a different option other than "DROP", this is a finding.

Check Content Reference

M

Target Key

5551