The validate_as_request function in kdc_util.c in the Key Distribution Center (KDC) in MIT Kerberos 5 (aka krb5) before 1.13.6 and 1.4.x before 1.14.3, when restrict_anonymous_to_tgt is enabled, uses an incorrect client data structure, which allows remote authenticated users to cause a denial of service (NULL pointer dereference and daemon crash) via an S4U2Self request.
krbdev.mit.edu/rt/Ticket/Display.html?id=8458
lists.opensuse.org/opensuse-updates/2016-09/msg00035.html
rhn.redhat.com/errata/RHSA-2016-2591.html
web.mit.edu/kerberos/krb5-1.13/
web.mit.edu/kerberos/krb5-1.14/
www.securityfocus.com/bid/92132
www.securitytracker.com/id/1036442
github.com/krb5/krb5/commit/93b4a6306a0026cf1cc31ac4bd8a49ba5d034ba7
lists.debian.org/debian-lts-announce/2018/01/msg00040.html
lists.fedoraproject.org/archives/list/[email protected]/message/AWL3KYFRJIX37EAM4DKCQQIQP2WBKL35/