STIGQter: STIG Summary: Canonical Ubuntu 24.04 LTS Security Technical Implementation Guide Version: 1 Release: 6 Benchmark Date: 01 Jul 2026:

Ubuntu 24.04 LTS must be configured to use TCP syncookies.

DISA Rule

SV-270753r1066748_rule

Vulnerability Number

V-270753

Group Title

SRG-OS-000142-GPOS-00071

Rule Version

UBTU-24-600190

Severity

CAT II

CCI(s)

CCI-001095 - Manage capacity, bandwidth, or other redundancy to limit the effects of information flooding types of denial of service attacks.

Weight

Fix Recommendation

Configure Ubuntu 24.04 LTS to use TCP syncookies with the following command:

$ sudo sysctl -w net.ipv4.tcp_syncookies=1

If "1" is not the system's default value, add or update the following line in "/etc/sysctl.conf":

net.ipv4.tcp_syncookies = 1

Check Contents

Verify Ubuntu 24.04 LTS is configured to use TCP syncookies with the following command:

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

If the value is not "1", this is a finding.

Check the saved value of TCP syncookies with the following command:

$ sudo grep -ir net.ipv4.tcp_syncookies /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf 2> /dev/null
/etc/sysctl.d/99-sysctl.conf:net.ipv4.tcp_syncookies=1
/etc/sysctl.conf:net.ipv4.tcp_syncookies=1

If the "net.ipv4.tcp_syncookies" option is not set to "1", is commented out, or is missing, this is a finding.

Vulnerability Number

V-270753

Documentable

False

Rule Version

UBTU-24-600190

Severity Override Guidance

Check Content Reference

Target Key

5673