Vulnerability Discussion

If compression is allowed in an SSH connection prior to authentication, vulnerabilities in the compression software could result in compromise of the system from an unauthenticated connection, potentially with root privileges.

Check

Note: If the installed version of OpenSSH is 7.4 or above, this requirement is not applicable.

Verify the SUSE operating system SSH daemon performs compression after a user successfully authenticates.

Check that the SSH daemon performs compression after a user successfully authenticates with the following command:

# sudo grep -i compression /etc/ssh/sshd_config
Compression delayed

If the "Compression" keyword is set to "yes", is missing, or the returned line is commented out, this is a finding.

Fix

Configure the SUSE operating system SSH daemon performs compression after a user successfully authenticates.

Uncomment the "Compression" keyword in "/etc/ssh/sshd_config" on the system and set the value to "delayed" or "no":

Compression no