Tak Ubuntu na to nejako ser... kasle:
16.04.3 LTS: jadro 4.4.0-109-generic #132-Ubuntu SMP Tue Jan 9 19:52:39 UTC 2018 x86_64
17.10: jadro 4.13.0-25-generic #29-Ubuntu SMP Mon Jan 8 21:14:41 UTC 2018 x86_64
Vsetko aktualne updaty. Ani v jednom pripade som adresar "vulnerabilities" v /sys/devices/system/cpu/ nenasiel
https://www.theinquirer.net/inquirer/news/3024277/canonical-reissues-second-meltdown-spectre-patch-for-ubuntu-after-borkage
https://insights.ubuntu.com/2018/01/12/meltdown-and-spectre-status-update/
https://wiki.ubuntu.com/SecurityTeam/KnowledgeBase/SpectreAndMeltdown
(ale to Tvůj problém zřejmě neřeší, přiznávám)