The SMB Signing not required when detected with a vulnerability scanner will report it as a CVSSv3.0 5.3.

CVSS is a scoring system for vulnerability systems, its an industry standard scoring system to mark findings against a specific number ranging from 0 to 10. They are shown as:

Signing is not required on the remote SMB server. Enforce message signing in the host's configuration. On Windows, this is found in the policy setting 'Microsoft network server: Digitally sign communications (always)'. On Samba, the setting is called 'server signing'.