Ken Johnson and Jann Horn independently discovered that microprocessors utilizing speculative execution of a memory read may allow unauthorized memory reads via sidechannel attacks. An attacker in the guest could use this to expose sensitive guest information, including kernel memory. This update allows libvirt to expose new CPU features added by microcode updates to guests. (CVE-2018-3639) Daniel P. Berrange discovered that libvirt incorrectly handled the QEMU guest agent. An attacker could possibly use this issue to consume resources, leading to a denial of service. (CVE-2018-1064)

It was discovered that microprocessors utilizing speculative execution and branch prediction may allow unauthorized memory reads via sidechannel attacks. This flaw is known as Spectre. An attacker in the guest could use this to expose sensitive guest information, including kernel memory. This update allows libvirt to expose new CPU features added by microcode updates to guests. On amd64 and i386, new CPU models that match the updated microcode features were added with an -IBRS suffix. Certain environments will require guests to be switched manually to the new CPU models after microcode updates have been applied to the host.