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RHEL-09-255085 RHEL 9 must not allow users to override SSH environment variables.

DISA STIG library V2R10
All changes in this version
first version loaded CAT II

Maps to CM-6 via CCI-000366

Title

RHEL 9 must not allow users to override SSH environment variables.

Control

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.

Discussion

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

Related controls

CCI-000366

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