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.
libraries/libldap/tls_o.c in OpenLDAP 2.2 and 2.4, and possibly other versions, when OpenSSL is used, does not properly handle a '\0' character in a domain name in the subject's Common Name (CN) field of an X.509 certificate, which allows man-in-the-middle attackers to spoof arbitrary SSL servers via a crafted certificate issued by a legitimate Certification Authority, a related issue to CVE-2009-2408.
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.