A flaw was found in 389-ds-base. When processing a ModifyDN (rename) request whose new relative distinguished name (RDN) uses an attribute's schema alias name (for example, "commonName") instead of its canonical name (for example, "cn"), the server fails to recognize that the aliased attribute already exists on the target entry. This causes the directory server to construct a duplicate, inconsistent internal attribute structure for the entry. A subsequent internal lookup against this inconsistent structure dereferences a NULL pointer, crashing the ns-slapd process. An authenticated user holding the "moddn" (rename) access control right on an entry can use this flaw to crash the directory server, resulting in a denial of service for all users of that directory server instance.