Linux 6.12 will again be a kernel with short long-term support

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Linux 6.12 has officially been chosen as the long-term kernel and will therefore receive security corrections not just for twelve weeks, but for at least two years. Possibly even more. It cannot be ruled out that it will end up being six, as with the 4.19.y kernel series, which was discontinued at the same time, but it is rather unlikely: the kernel developers are currently slowly reducing the period for Long Term Support (LTS). According to the kernel developers, Linux series that are more than one or two years old are unsuitable for general-purpose servers anyway, as they do not plug some gaps or only do so poorly.

LTS support is gradually shrinking to an old level

It was almost certain that the Linux version fulfilling modern real-time requirements for the first time would be a longterm kernel: Greg Kroah-Hartman has always chosen the last mainline version of a year as such for years. This time it will be the recently released 6.12, as 6.13 will not be released until January 20 or 27.

The developer of the "stable team" has set the end of the support period at the end of 2026 for the time being. In other words, at the same time as support for the 5.10.y, 5.15.y, 6.1.y and 6.6.y series expires. This concentration is due to a gradual shortening of the maintenance periods to the originally envisaged two years, after several years of longterm kernel support, most of which ended up with six years of support. This was thanks to companies such as Google, which support the stable team in its work behind the scenes.

Lack of support

If enough sponsors can be found again, Kroah-Hartman may even extend the support period for some series. On the one hand, it looks as though this will not happen with 6.12, as only a few companies are generally willing to make such arrangements. Google is also losing interest in this more and more, as it will occasionally upgrade the kernel on its Pixel devices to a newer series from now on. On the other hand, the next version of Debian will probably use Linux 6.12, so it could well be that their kernel maintainers will not only maintain the 6.12 series in their distribution, but also as part of Kernel.org over a longer period of time. This has already been the case several times when longterm kernels only received two years of maintenance, most recently with Linux 3.16.y.

Parallel to the announcement of the new longterm series, the stable team has discontinued maintenance of the 6.11.y and 4.19.y series: Kroah-Hartman advises users to switch to newer version series. For most users, this is not or only indirectly relevant, as the distributor is responsible for updating the kernel with security vulnerabilities. Some, such as Ubuntu, often rely for years on versions that the Linux developers have abandoned after just a few weeks. It is unclear how thorough the maintenance of such distributions is in times of around 55 CVEs per week.

Old longterm kernels unsuitable for generic systems

But even 4.19.y was by no means completely secure: in the announcement, Kroah-Hartman mentions that almost a thousand with corrections were left out, even though they received a CVE flag. This happens because sometimes nobody makes the effort to adapt changes to the code of such old kernel series. Sometimes gaps are only poorly plugged.

Kroah-Hartman points out these aspects from time to time. He often emphasizes that several years of longterm kernels are only intended for devices that are under full control or use an extremely strong security model like Android. Devices with virtual machines or untrusted users, on the other hand, should always use the latest stable or longterm kernel. In other words: Until recently, Linux 6.11.y or 6.6.y would have been the appropriate series, from now on it is 6.12.y –, although this in no way implies that you have to switch head over heels from LTS kernel 6.6.y to 6.12.y now.

(mki)