Title

The SSH daemon must not allow compression or must only allow compression after successful authentication. (Cat II impact)

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 Content

Check the SSH daemon configuration for the compression setting. # grep -i Compression /etc/ssh/sshd_config | egrep "no|delayed" If the setting is missing or is commented out, this is a finding. If the setting is present but is not set to "no" or "delayed", this is a finding.

Fix Text

Edit the SSH daemon configuration and add or edit the "Compression" setting value to "no" or "delayed". Restart the SSH daemon. # /sbin/service sshd restart

Additional Identifiers

Rule ID: SV-46107r2_rule

Vulnerability ID: V-22488

Group Title: GEN005539

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.