Cis Ubuntu1604 V200 5 3 13

---
name: cis-ubuntu1604-v200-5-3-13
description: "Ensure SSH PermitUserEnvironment is disabled"
category: cis-networking
version: "2.0.0"
author: cyberstrike-official
tags: [cis, ubuntu, linux, ubuntu-16.04, ssh, remote-access]
cis_id: "5.3.13"
cis_benchmark: "CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0"
tech_stack: [ubuntu, linux]
cwe_ids: []
chains_with: []
prerequisites: []
severity_boost: {}
---

# CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0 - Control 5.3.13

## Description

The `PermitUserEnvironment` option allows users to present environment options to the `ssh` daemon.

## Rationale

Permitting users the ability to set environment variables through the SSH daemon could potentially allow users to bypass security controls (e.g. setting an execution path that has `ssh` executing a Trojan's programs).

## Audit Procedure

### Command Line

Run the following command and verify that output matches:

```bash
sshd -T -C user=root -C host="$(hostname)" -C addr="$(grep $(hostname) /etc/hosts | awk '{print $1}')" | grep permituserenvironment
```

### Expected Result

```
permituserenvironment no
```

Run the following command and verify the output:

```bash
grep -Ei '^\s*PermitUserEnvironment\s+yes' /etc/ssh/sshd_config
```

Nothing should be returned.

## Remediation

### Command Line

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

```
PermitUserEnvironment no
```

## Default Value

PermitUserEnvironment no

## References

1. SSHD_CONFIG(5)

## CIS Controls

Version 7

5.1 Establish Secure Configurations - Maintain documented, standard security configuration standards for all authorized operating systems and software.

## Profile Applicability

- Level 1 - Server
- Level 1 - Workstation

## Assessment Status

Automated