This warning advisory is relevant for users of systems with the Intel processors code-named "Skylake" and "Kaby Lake". These are: the 6th and 7th generation Intel Core processors (desktop, embedded, mobile and HEDT), their related server processors (such as Xeon v5 and Xeon v6), as well as select Intel Pentium processor models.

TL;DR: unfixed Skylake and Kaby Lake processors could, in some situations, dangerously misbehave when hyper-threading is enabled. Disable hyper-threading immediately in BIOS/UEFI to work around the problem. Read this advisory for instructions about an Intel-provided fix.

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...it could cause spurious errors, such as application and system misbehavior, data corruption, and data loss.

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Please note that the defect can potentially affect any operating system (it is not restricted to Debian, and it is not restricted to Linux-based systems).