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The Ubuntu operating system must not allow users to override SSH environment variables.


Overview

Finding ID Version Rule ID IA Controls Severity
V-98989 UBTU-16-030251 SV-108093r1_rule Medium
Description
Failure to restrict system access to authenticated users negatively impacts Ubuntu operating system security.
STIG Date
Canonical Ubuntu 16.04 Security Technical Implementation Guide 2019-12-23

Details

Check Text ( C-97831r1_chk )
Verify the operating system does not allow users to override environment variables to the SSH daemon.

Check for the value of the "PermitUserEnvironment" keyword with the following command:

# grep -i permituserenvironment /etc/ssh/sshd_config
PermitUserEnvironment no

If the "PermitUserEnvironment" keyword is not set to "no", is missing, or is commented out, this is a finding.
Fix Text (F-104665r1_fix)
Configure the operating system to not allow users to override environment variables to the SSH daemon.

Edit the "/etc/ssh/sshd_config" file to uncomment or add the line for "PermitUserEnvironment" keyword and set the value to "no":

PermitUserEnvironment no

The SSH service must be restarted for changes to take effect:

# sudo systemctl restart sshd.service