Vulnerability Discussion

If an unauthorized user obtains the private SSH host key file, the host could be impersonated.

Check

Verify the SSH private host key files have mode "0640" or less permissive.

The following command will find all SSH private key files on the system and list their modes:

# find / -name '*ssh_host*key' | xargs ls -lL

-rw-r----- 1 root ssh_keys 112 Apr 1 11:59 ssh_host_dsa_key
-rw-r----- 1 root ssh_keys 202 Apr 1 11:59 ssh_host_key
-rw-r----- 1 root ssh_keys 352 Apr 1 11:59 ssh_host_rsa_key

If any file has a mode more permissive than "0640", this is a finding.

Fix

Configure the mode of SSH private host key files under "/etc/ssh" to "0640" with the following command:

# chmod 0640 /path/to/file/ssh_host*key