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 | grep -v '^#' If the setting is not present, or set to yes, this is a finding.

Fix Text

Edit the SSH daemon configuration and add or edit the Compression setting value to no or delayed.

Additional Identifiers

Rule ID: SV-226999r603265_rule

Vulnerability ID: V-226999

Group Title: SRG-OS-000480

Expert Comments

CCIs tied to check.

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