A heap buffer overflow flaw was found in QEMU's Cirrus CLGD 54xx VGA emulator's VNC display driver support before 2.9; the issue could occur when a VNC client attempted to update its display after a VGA operation is performed by a guest. A privileged user/process inside a guest could use this flaw to crash the QEMU process or, potentially, execute arbitrary code on the host with privileges of the QEMU process.
https://support.citrix.com/article/CTX221578
https://security.gentoo.org/glsa/201706-03
https://lists.debian.org/debian-lts-announce/2018/09/msg00007.html
https://lists.debian.org/debian-lts-announce/2018/02/msg00005.html
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2016-9603
https://access.redhat.com/errata/RHSA-2017:1441
https://access.redhat.com/errata/RHSA-2017:1206
https://access.redhat.com/errata/RHSA-2017:1205
https://access.redhat.com/errata/RHSA-2017:0988
https://access.redhat.com/errata/RHSA-2017:0987
https://access.redhat.com/errata/RHSA-2017:0985
https://access.redhat.com/errata/RHSA-2017:0984
https://access.redhat.com/errata/RHSA-2017:0983
https://access.redhat.com/errata/RHSA-2017:0982
https://access.redhat.com/errata/RHSA-2017:0981
https://access.redhat.com/errata/RHSA-2017:0980