CVE-2016-9603: Citrix Xenserver

Critical severity, CVSS 9.9. EPSS: 4.4% chance of exploitation in the next 30 days.

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.

Affected products

• Citrix Xenserver: version 6.0.2 only; version 6.2.0 only; version 6.5 only; version 7.0 only; version 7.1 only
• Debian Debian Linux: version 7.0 only
• Qemu Qemu: before 2.9.0 (fixed in 2.9.0)
• Red Hat Enterprise Linux Desktop: version 6.0 only; version 7.0 only
• Red Hat Enterprise Linux Server: version 6.0 only; version 7.0 only
• Red Hat Enterprise Linux Server Aus: version 7.3 only; version 7.4 only
• Red Hat Enterprise Linux Server Eus: version 7.3 only; version 7.4 only; version 7.5 only
• Red Hat Enterprise Linux Workstation: version 6.0 only; version 7.0 only
• Red Hat Openstack: version 5.0 only; version 6.0 only; version 7.0 only; version 8 only; version 9 only; version 10 only

Published 2018-07-27. Last modified 2026-06-17.