cis-ubuntu1804-v220-4-2-17

name	cis-ubuntu1804-v220-4-2-17
description	Ensure sshd MaxStartups is configured
category	cis-networking
version	2.2.0
author	cyberstrike-official
tags	["cis","ubuntu","linux","ubuntu-18.04","ssh","remote-access"]
cis_id	4.2.17
cis_benchmark	CIS Ubuntu Linux 18.04 LTS Benchmark v2.2.0
tech_stack	["ubuntu","linux"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

CIS Ubuntu Linux 18.04 LTS Benchmark v2.2.0 - Control 4.2.17

Profile Applicability

• Level 1 - Server
• Level 1 - Workstation

Description

The MaxStartups parameter specifies the maximum number of concurrent unauthenticated connections to the SSH daemon.

Rationale

To protect a system from denial of service due to a large number of pending authentication connection attempts, use the rate limiting function of MaxStartups to protect availability of sshd logins and prevent overwhelming the daemon.

Audit Procedure

Command Line

Run the following command and verify the output:

sshd -T | grep -i maxstartups

Expected Result

maxstartups 10:30:60

OR more restrictive.

Remediation

Command Line

Edit the /etc/ssh/sshd_config file to set the parameter as follows:

MaxStartups 10:30:60

Default Value

MaxStartups 10:30:100

References

1. NIST SP 800-53 Rev. 5: CM-6

CIS Controls

None

Profile Applicability

• Level 1 - Server
• Level 1 - Workstation

Assessment Status

Automated