Security researchers have developed methods involving speculative execution to read kernel memory from user space on a variety of processors from a range of vendors produced in the last decade. These methods have been referred to as Meltdown and Spectre.
Meltdown is described as a vulnerability that allows a program to access the memory, and thus also the secrets, of other programs and the operating system. Meltdown only impacts Intel chips.
Spectre allows access to protected memory of other applications. Spectre impacts Intel, AMD and ARM chips, which includes some mobile devices.