Security researchers from Microsoft and Google have discovered a fourth variant of the data-leaking Meltdown-Spectre security flaws impacting modern CPUs in millions of computers, including those marketed by Apple.
Variant 4 comes weeks after German computer magazine Heise reported about a set of eight Spectre-class vulnerabilities in Intel CPUs and a small number of ARM processors, which may also impact AMD processor architecture as well.
Variants 1 and 2 (CVE-2017-5753 and CVE-2017-5715), known as Spectre, and Variant 3 (CVE-2017-5754), known as Meltdown, are three processor vulnerabilities disclosed by Google Project Zero researchers in January this year.
Now, Microsoft and Google researchers have disclosed Variant 4 (CVE-2018-3639), dubbed Speculative Store Bypass, which is a similar Spectre variant that takes advantage of speculative execution that modern CPUs use to potentially expose sensitive data through a side channel.
Speculative execution is a core component of modern processors design that speculatively executes instructions based on assumptions that are considered likely to be true. If the assumptions come out to be valid, the execution continues and is discarded if not.
However, the speculative-execution design blunders can be exploited by malicious software or apps running on a vulnerable computer, or a nefarious actor logged into the system, to trick the CPU into revealing sensitive information, like passwords and encryption keys, stored in system memory and the kernel.
Unlike Meltdown that primarily impacted Intel chips, Spectre affects chips from other manufacturers as well.
Spectre and Meltdown Continues to Haunt Intel, AMD, ARM
The latest Variant 4 flaw affects modern processor cores from Intel, AMD, and ARM, as well as IBM’s Power 8, Power 9, and System z CPUs—threatening almost all PCs, laptops, smartphones, tablets, and embedded electronics regardless of manufacturer or operating system.
Linux distro giant Red Hat has also provided a video outlining the new Spectre flaw, alongside publishing a substantial guide: