A use-after-free vulnerability was found in the way the Linux kernel#039;s KVM hypervisor implements its device control API. While creating a device via kvm_ioctl_create_device, the device holds a reference to a VM object, later this reference is transferred to the caller#039;s file descriptor table. If such file descriptor was to be closed, reference count to the VM object could become zero, potentially leading to a use-after-free issue. A user/process could use this flaw to crash the guest VM resulting in a denial of service issue or, potentially, gain privileged access to a system.An information leakage issue was found in the way Linux kernel#039;s KVM hypervisor handled page fault exceptions while emulating instructions like VMXON, VMCLEAR, VMPTRLD, and VMWRITE with memory address as an operand. It occurs if the operand is a mmio address, as the returned exception object holds uninitialized stack memory contents. A guest user/process could use this flaw to leak host#039;s stack memory contents to a guest.A use-after-free vulnerability was found in the way the Linux kernel#039;s KVM hypervisor emulates a preemption timer for L2 guests when nested virtualization is enabled. This high resolution timer runs when a L2 guest is active. After VM exit, the sync_vmcs12 timer object is stopped. The use-after-free occurs if the timer object is freed before calling sync_vmcs12 routine. A guest user/process could use this flaw to crash the host kernel resulting in a denial of service or, potentially, gain privileged access to a system.