Are passwordless logins like ##MS_SQLResourceSigningCertificate## , ##MS_AgentSigningCertificate## a vulnerability?

Question

I'm new to MS SQL Server.

Colleagues working in IT security, have run an scan showing come DB users with null password.

Some of them are ( # included )

##MS_SQLResourceSigningCertificate##
##MS_SQLReplicationSigningCertificate##
##MS_SQLAuthenticatorCertificate##
##MS_PolicySigningCertificate##
##MS_SmoExtendedSigningCertificate##
##MS_AgentSigningCertificate##

I suspect they are not a security threat but, since they don't use Windows Authentication either, I don't know how to support that assumption.

What are these logins for ?