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.
https://support.apple.com/kb/HT210788
https://support.apple.com/HT204659
https://seclists.org/bugtraq/2019/Dec/23
https://exchange.xforce.ibmcloud.com/vulnerabilities/100937
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=776988
http://www.securitytracker.com/id/1032399
http://www.securityfocus.com/bid/72519
http://www.oracle.com/technetwork/topics/security/bulletinjul2015-2511963.html
http://www.openwall.com/lists/oss-security/2015/02/07/3
http://www.mandriva.com/security/advisories?name=MDVSA-2015:074
http://www.mandriva.com/security/advisories?name=MDVSA-2015:073
http://www.debian.org/security/2015/dsa-3209
http://secunia.com/advisories/62787
http://seclists.org/fulldisclosure/2019/Dec/26
http://lists.opensuse.org/opensuse-updates/2015-07/msg00069.html
http://lists.apple.com/archives/security-announce/2015/Apr/msg00001.html