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 QEMU to expose new CPU features added by microcode updates to guests on amd64 and i386.
2.0.0+dfsg-2ubuntu1.421:2.5+dfsg-5ubuntu10.291:2.11+dfsg-1ubuntu7.2