modrdn.c in slapd in OpenLDAP 2.4.x before 2.4.24 allows remote attackers to cause a denial of service (daemon crash) via a relative Distinguished Name (DN) modification request (aka MODRDN operation) that contains an empty value for the OldDN field.
chain.c in back-ldap in OpenLDAP 2.4.x before 2.4.24, when a master-slave configuration with a chain overlay and ppolicy_forward_updates (aka authentication-failure forwarding) is used, allows remote authenticated users to bypass external-program authentication by sending an invalid password to a slave server.
bind.cpp in back-ndb in OpenLDAP 2.4.x before 2.4.24 does not require authentication for the root Distinguished Name (DN), which allows remote attackers to bypass intended access restrictions via an arbitrary password.
pam_ldap and nss_ldap, when used with OpenLDAP and connecting to a slave using TLS, does not use TLS for the subsequent connection if the client is referred to a master, which may cause a password to be sent in cleartext and allows remote attackers to sniff the password.