CVE-2015-3611: 
Fortinet FortiManager vulnerability analysis and mitigation

A race condition vulnerability identified as CVE-2015-3611 was discovered in the Linux kernel's KVM (Kernel-based Virtual Machine) subsystem. The vulnerability was reported by Lars Bull of Google and was disclosed in early 2015 (Red Hat Advisory).

The vulnerability exists in the way the Linux kernel's KVM subsystem handled PIT (Programmable Interval Timer) emulation. The flaw was rated as having Important security impact by Red Hat Product Security (Red Hat Advisory).

When exploited, this vulnerability allows a guest user who has access to the PIT I/O ports to crash the host system (Red Hat Advisory).

Red Hat released updated kvm packages containing backported patches to address this vulnerability. The mitigation requires stopping all KVM guest virtual machines, either rebooting the hypervisor machine or removing and reloading the affected modules (kvm, ksm, kvm-intel or kvm-amd), and then restarting the KVM guest virtual machines (Red Hat Advisory).