Samba AD DC S4U2Self Crash in experimental

Description

A user in a Samba AD domain can crash the KDC when Samba is built in
the non-default MIT Kerberos configuration.

With this advisory we clarify that the MIT Kerberos build of the Samba
AD DC is considered experimental. Therefore the Samba Team will not
issue security patches for this configuration.

Patch Availability

Patches addressing parts of this issue have been posted to:

https://bugzilla.samba.org/show_bug.cgi?id=13571

Additionally, Samba 4.7.12, 4.8.7 and 4.9.3 have been issued as
security releases to prevent building of the AD DC with MIT Kerberos
unless --with-experimental-mit-ad-dc is specified to the configure
command. Samba administrators are advised to recompile Samba with the
default internal Heimdal Kerberos build as soon as possible by
removing --with-system-mitkrb5 from the configure command and
rebuilding Samba.

Workaround and mitigation

The default Heimdal build of Samba is not vulnerable.

Credits

Originally reported by Isaac Boukris.

Patches to disable the build provided by Andrew Bartlett of Catalyst
and the Samba team.

== Our Code, Our Bugs, Our Responsibility.
== The Samba Team