CVE-2019-14870

All Samba versions 4.x.x before 4.9.17, 4.10.x before 4.10.11 and 4.11.x
before 4.11.3 have an issue, where the S4U (MS-SFU) Kerberos delegation
model includes a feature allowing for a subset of clients to be opted out
of constrained delegation in any way, either S4U2Self or regular Kerberos
authentication, by forcing all tickets for these clients to be
non-forwardable. In AD this is implemented by a user attribute
delegation_not_allowed (aka not-delegated), which translates to
disallow-forwardable. However the Samba AD DC does not do that for S4U2Self
and does set the forwardable flag even if the impersonated client has the
not-delegated flag set.

Bugs

• <https://bugzilla.samba.org/show_bug.cgi?id=14187&gt;