The deref_parseCtrl function in servers/slapd/overlays/deref.c in OpenLDAP 2.4.13 through 2.4.40 allows remote attackers to cause a denial of service (NULL pointer dereference and crash) via an empty attribute list in a deref control in a search request.<a href=http://cwe.mitre.org/data/definitions/476.html>CWE-476: NULL Pointer Dereference</a> http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2015-1545