KVM is a full virtualization solution for Linux on AMD64 and Intel 64 systems. The qemu-kvm package provides the user-space component for running virtual machines using KVM. A heap-based buffer overflow flaw was discovered in the way QEMU"s AMD PC-Net II Ethernet Controller emulation received certain packets in loopback mode. A privileged user inside a guest could use this flaw to crash the host QEMU process or, potentially, execute arbitrary code with privileges of the host QEMU process. A buffer overflow flaw was found in the way QEMU"s AMD PC-Net II emulation validated certain received packets from a remote host in non-loopback mode. A remote, unprivileged attacker could potentially use this flaw to execute arbitrary code on the host with the privileges of the QEMU process. Note that to exploit this flaw, the guest network interface must have a large MTU limit. Red Hat would like to thank Qinghao Tang of QIHU 360 Marvel Team and Ling Liu of Qihoo 360 Inc. for reporting the CVE-2015-7504 issue, and Ling Liu of Qihoo 360 Inc. for reporting the CVE-2015-7512 issue. The CVE-2015-7512 issue was independently discovered by Jason Wang of Red Hat. All qemu-kvm users are advised to upgrade to these updated packages, which contain backported patches to correct these issues. After installing this update, shut down all running virtual machines. Once all virtual machines have shut down, start them again for this update to take effect.