The SSH daemon must not allow compression or must only allow compression after successful authentication.

From Oracle Linux 5 Security Technical Implementation Guide

Associated with: CCI-000366

SV-64089r1_rule The SSH daemon must not allow compression or must only allow compression after successful authentication.

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 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

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