A stack buffer overflow flaw was found in 389 Directory Server (389-ds-base). The get_ruvelement_from_berval() function in repl5_ruv.c copies digit characters from a network-supplied RUV berval into a fixed 16-byte stack buffer without bounds checking. A remote unauthenticated attacker can crash the LDAP server by sending a crafted StartNSDS50ReplicationRequest extended operation containing a replica ID field with more than 16 digit characters. The overflow occurs during payload decoding, before any authorization check. Stack protectors limit impact to denial of service.
Disable anonymous access by setting nsslapd-allow-anonymous-access to 'off' or 'rootdse' in cn=config. Alternatively, restrict network access to the LDAP port to trusted replication partners only using firewall rules.