Do you use "database ldbm" in slapd.conf? The LDAP Compare operation can make it crash that way. (Since OpenLDAP 2.3.16; back-ldbm/compare.c rev 1.53.) I've committed a fix: http://www.openldap.org/devel/cvsweb.cgi/servers/slapd/back-ldbm/Attic/compa... BDB more reliable. LDBM has been removed in OpenLDAP 2.4.