It was found that sssd's sysdb_search_user_by_upn_res() function before 1.16.0 did not sanitize requests when querying its local cache and was vulnerable to injection. In a centralized login environment, if a password hash was locally cached for a given user, an authenticated attacker could use this flaw to retrieve it.
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2017-12173