RHEL 9 must not allow users to override SSH environment variables.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
| V-257993 | RHEL-09-255085 | SV-257993r1045049_rule | Medium |
| Description |
| SSH environment options potentially allow users to bypass access restriction in some configurations. |
| STIG | Date |
| Red Hat Enterprise Linux 9 Security Technical Implementation Guide | 2024-12-04 |
Details
| Check Text (C-61734r952191_chk) |
| 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. If the required value is not set, this is a finding. |
| Fix Text (F-61658r1045048_fix) |
| Configure the RHEL 9 SSH daemon to not allow unattended or automatic logon to the system by editing 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 |