STIGQter: STIG Summary: Oracle Linux 9 Security Technical Implementation Guide Version: 1 Release: 6 Benchmark Date: 01 Jul 2026:

OL 9 must be configured to use TCP syncookies.

DISA Rule

SV-271884r1208735_rule

Vulnerability Number

V-271884

Group Title

SRG-OS-000420-GPOS-00186

Rule Version

OL09-00-006050

Severity

CAT II

CCI(s)

• CCI-002385 - Protect against or limit the effects of organization-defined types of denial of service events.
• CCI-001095 - Manage capacity, bandwidth, or other redundancy to limit the effects of information flooding types of denial of service attacks.

Weight

10

Fix Recommendation

Configure OL 9 to use TCP syncookies.

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

net.ipv4.tcp_syncookies = 1

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

$ sudo sysctl --system

Check Contents

Verify OL 9 is configured to use IPv4 TCP syncookies.

Determine if syncookies are used with the following command:

$ sysctl net.ipv4.tcp_syncookies
net.ipv4.tcp_syncookies = 1

If the network parameter "ipv4.tcp_syncookies" is not equal to "1" or nothing is returned, this is a finding.

Vulnerability Number

V-271884

Documentable

False

Rule Version

OL09-00-006050

Severity Override Guidance

Verify OL 9 is configured to use IPv4 TCP syncookies.

Determine if syncookies are used with the following command:

$ sysctl net.ipv4.tcp_syncookies
net.ipv4.tcp_syncookies = 1

If the network parameter "ipv4.tcp_syncookies" is not equal to "1" or nothing is returned, this is a finding.

Check Content Reference

M

Target Key

5680