Introduced this year with the Linux 6.16 kernel was the new functionality for reporting to users when running on outdated Intel CPU microcode since it can pose security vulnerability issues and/or functionality problems. The Linux kernel support for propagating this "old_microcode" reporting via sysfs relies on a static list of microcode versions corresponding to different Intel CPU generations. For the Linux 6.18 kernel this list is being updated to reflect modern baselines for Intel recommendations on CPU microcode.

Sent in via the x86/microcode pull request is refreshing the revisions of Intel CPU microcode for determining the old microcode versions. In particular, it updates against the Intel CPU microcode versions published in May with the Intel CPU microcode 20250512 release.

Intel published their May 2025 CPU microcode updates mainly due to the Training Solo security issue . The May microcode updates covered from Intel Lunar Lake back through 8th Gen Core CPUs. For server CPUs from 2nd Gen Xeon Scalable through the newest Xeon 6 processors.

So if your Intel Linux systems are running CPU microcode prior to the May 2025 release, beginning on Linux 6.18 that will now be propagated to user-space with the updated "old_microcode" handling to make sure users/administrators are aware.