MediumSSHBLWK-SSH-008

SSH StrictModes is disabled

What this means

StrictModes is set to “‹strict modes›” in sshd_config. With StrictModes off, sshd no longer verifies that a user's home directory and key files have safe ownership and permissions before trusting them — a world-writable home directory or key file then becomes a usable login bypass instead of a rejected, obviously-broken config.

How to fix it

Set StrictModes yes in /etc/ssh/sshd_config and run systemctl restart sshd.

Check it yourself

Run a scan and look for BLWK-SSH-008 in the results:

bulwark scan

Installed the standalone CLI package instead of the app? The command is bulwarkctl.

How Bulwark decides

Bulwark reads sshd_config and reports this check when:

strict_modes == "no"

If a value can't be read, Bulwark reports the check as undetermined rather than passing it. View the rule source.

References

• CIS Benchmark 5.2.9

Related checks

• SSH password authentication is enabled · BLWK-SSH-001
• SSH root login is permitted · BLWK-SSH-002
• SSH allows empty passwords · BLWK-SSH-003
• SSH X11 forwarding is enabled · BLWK-SSH-004
• SSH TCP forwarding/tunneling is enabled · BLWK-SSH-005
• SSH permits user-set environment variables · BLWK-SSH-006