The ne2000_receive function in the NE2000 NIC emulation support (hw/net/ne2000.c) in QEMU before 2.5.1 allows local guest OS administrators to cause a denial of service (infinite loop and QEMU process crash) via crafted values for the PSTART and PSTOP registers, involving ring buffer control.
https://bugzilla.redhat.com/show_bug.cgi?id=1303106
https://lists.debian.org/debian-lts-announce/2018/11/msg00038.html
https://lists.gnu.org/archive/html/qemu-devel/2016-02/msg06126.html
https://security.gentoo.org/glsa/201609-01