The authentication_agent_new function in polkitbackend/polkitbackendinteractiveauthority.c in PolicyKit (aka polkit) before 0.113 allows local users to cause a denial of service (NULL pointer dereference and polkitd daemon crash) by calling RegisterAuthenticationAgent with an invalid object path.
lists.freedesktop.org/archives/polkit-devel/2015-July/000432.html
lists.freedesktop.org/archives/polkit-devel/2015-May/000420.html
lists.freedesktop.org/archives/polkit-devel/2015-May/000421.html
lists.opensuse.org/opensuse-security-announce/2015-10/msg00010.html
lists.opensuse.org/opensuse-updates/2015-11/msg00042.html
www.securityfocus.com/bid/76086
www.securitytracker.com/id/1035023
lists.fedoraproject.org/pipermail/package-announce/2015-July/161721.html
lists.fedoraproject.org/pipermail/package-announce/2015-July/162294.html
usn.ubuntu.com/3717-1/