A flaw was found in 389 Directory Server. The dereference control plugin does not check for allocation failure before using a BER structure, allowing an unauthenticated remote attacker to crash the LDAP server when the system is under memory pressure.
Disable the deref plugin (most effective): dsconf <instance> plugin deref disable; systemctl restart dirsrv@<instance>. Disable anonymous access (nsslapd-allow-anonymous-access=off) to raise the bar from pre-auth to authenticated exploitation. Configure memory limits as defense-in-depth: set nsslapd-maxbersize and nsslapd-conntablesize, and deploy in a cgroup with memory limits.