Security researchers from Google and Microsoft have found two new variants of the Spectre attack that affects processors made by AMD, ARM, IBM, and Intel.
Rumors about this new flaw leaked online at the start of the month in a German magazine, but actual details were published today.
AMD,
ARM,
Intel,
Microsoft, and
Red Hat have published security advisories at the time of writing, containing explanations of how the bugs work, along with mitigation advice.
Bug known as SpectreNG
The bugs —referred to in the past weeks as SpectreNG— are related to the previous Meltdown and Spectre bugs discovered last year and announced at the start of 2018.
Both Google and Microsoft researchers discovered the bug independently. The bugs work similarly to the Meltdown and Spectre bugs, a reason why they were classified as "variant 3a" and "variant 4" instead of separate vulnerabilities altogether.
Variant 1: bounds check bypass (CVE-2017-5753) aka Spectre v1
Variant 2: branch target injection (CVE-2017-5715) aka Spectre v2
Variant 3: rogue data cache load (CVE-2017-5754) aka Meltdown
Variant 3a: rogue system register read (CVE-2018-3640)
Variant 4: speculative store bypass (CVE-2018-3639)
The most important of these two is Variant 4. Both bugs occur for the same reason —
speculative execution— a feature found in all modern CPUs that has the role of improving performance by computing operations in advance and later discarding unneeded data.