Vulnerability Discussion

SSH environment options potentially allow users to bypass access restriction in some configurations.

Check

Verify that OL 9 does not allow users to override SSH environment variables.

Verify that unattended or automatic logon via SSH is disabled with the following command:

$ sudo /usr/sbin/sshd -dd 2>&1 | awk '/filename/ {print $4}' | tr -d '\r' | tr '\n' ' ' | xargs sudo grep -iH '^\s*permituserenvironment'
PermitUserEnvironment no

If "PermitUserEnvironment" is set to "yes", is missing completely, or is commented out, this is a finding.

Fix

Configure the OL 9 SSH daemon to not allow unattended or automatic logon to the system.

Add or edit the following line in the "/etc/ssh/sshd_config" or in a file in "/etc/ssh/sshd_config.d":

PermitUserEnvironment no

Restart the SSH daemon for the setting to take effect:

$ sudo systemctl restart sshd.service