In OpenLDAP through 2.4.57 and 2.5.x through 2.5.1alpha, an assertion failure in slapd can occur in the issuerAndThisUpdateCheck function via a crafted packet, resulting in a denial of service (daemon exit) via a short timestamp. This is related to schema_init.c and checkTime.
https://www.debian.org/security/2021/dsa-4860
https://security.netapp.com/advisory/ntap-20210319-0005/
https://lists.debian.org/debian-lts-announce/2021/02/msg00035.html
https://git.openldap.org/openldap/openldap/-/commit/9badb73425a67768c09bcaed1a9c26c684af6c30
https://git.openldap.org/openldap/openldap/-/commit/3539fc33212b528c56b716584f2c2994af7c30b0