cis-ubuntu1804-v220-4-2-16

name	cis-ubuntu1804-v220-4-2-16
description	Ensure sshd MaxSessions is configured
category	cis-networking
version	2.2.0
author	cyberstrike-official
tags	["cis","ubuntu","linux","ubuntu-18.04","ssh","remote-access"]
cis_id	4.2.16
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 4.2.16

Profile Applicability

• Level 1 - Server
• Level 1 - Workstation

Description

The MaxSessions parameter specifies the maximum number of open sessions permitted from a given connection.

Rationale

To protect a system from denial of service due to a large number of concurrent sessions, use the rate limiting function of MaxSessions 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 maxsessions

Expected Result

maxsessions 10

Value should be 10 or less.

Remediation

Command Line

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

MaxSessions 10

Default Value

MaxSessions 10

References

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

CIS Controls

None

Profile Applicability

• Level 1 - Server
• Level 1 - Workstation

Assessment Status

Automated