The rtl8139_cplus_transmit function in hw/net/rtl8139.c in QEMU (aka Quick Emulator) allows local guest OS administrators to cause a denial of service (infinite loop and CPU consumption) by leveraging failure to limit the ring descriptor count.
http://lists.opensuse.org/opensuse-updates/2016-12/msg00140.html
https://access.redhat.com/errata/RHSA-2017:2392
https://access.redhat.com/errata/RHSA-2017:2408
https://lists.debian.org/debian-lts-announce/2018/11/msg00038.html
https://lists.gnu.org/archive/html/qemu-devel/2016-10/msg05495.html
https://security.gentoo.org/glsa/201611-11