The local_handler_callback function in server/responder/pam/pam_LOCAL_domain.c in sssd 0.4.1 does not properly handle blank-password accounts in the SSSD BE database, which allows context-dependent attackers to obtain access by sending the account's username, in conjunction with an arbitrary password, over an ssh connection.
https://www.redhat.com/archives/fedora-package-announce/2009-July/msg01236.html
https://exchange.xforce.ibmcloud.com/vulnerabilities/52210
https://bugzilla.redhat.com/show_bug.cgi?id=514057