Greg Kroah-Hartman signed off on four LTS kernels, 6.6.159, 6.1.190, 5.15.223 and 5.10.272, each carrying the same small set of backported networking and security fixes. The updates close a TCP use-after-free, harden IPv4 checksum validation and restore SCTP traffic through nfnetlink_queue, clearing the thresholds of Canadian advisory AV26-970. Two of the branches, 5.10 and 5.15, sit just two months from end of life on December 31, 2026, intensifying migration pressure for Ubuntu 22.04 and RHEL 9 users. The other two, 6.1 and 6.6, remain safe through the end of 2027, making this a planning window rather than a panic.

Four Linux LTS Kernels Ship Together as Two Race Toward End of Life

Greg Kroah-Hartman signed off on four Long-Term Support kernels within three minutes of each other today. They are 6.6.159, 6.1.190, 5.15.223 and 5.10.272. Not much happened in any of them. That's the whole point.

There's plenty of noise around the newest feature releases, but this week's story is quieter and arguably more important. These four are the mature branches that most production systems actually run on, the dependable, boring backbone of enterprise and cloud Linux. Two of them are just two months from losing upstream support, though, and that deadline is beginning to loom.

A lean cycle, shared fixes

Each of the four changelogs on kernel.org is thin. Drop the version bumps and you're left with essentially the same three networking and security patches carried across every tree. That's textbook mid-life LTS work. It also means the diff is small enough to review before your coffee cools.

The first is a use-after-free in the IPv4 TCP request-socket path, fixed by Eric Dumazet. Because request sockets now run without the listener lock, another CPU can free a child socket while a SYNACK is still being assembled. The patch defers cleanup to an RCU grace period instead. This one is reportedly spotted by Xinyang Ge of Anthropic, which matters since remote-triggerable memory bugs in the networking path are exactly the fun kind for attackers to play with.

Michael Tsirkin wrote the second fix. A packet carrying bad checksum metadata can wreck the network header mid-processing, or as he puts it, produce "a bunch of mischief." His patch adds a validation step before the checksum completes.

Antonio Ojea's third fix is older, just carried forward: it restores SCTP traffic flowing through nfnetlink_queue when GSO is enabled. It's a correctness fix for people running offloading stacks that mix nft_queue with GSO and SCTP, so most won't notice. But it's there, and it's real.

That leaves this week's releases squarely in "networking and security refresh" territory rather than a feature drop. Which, again, is what you'd expect.

The two-month clock

Here's the bigger picture. In 2023 the kernel maintainers cut standard LTS support from six years down to two, largely to keep everyone from burning out. The pushback was sharp and fast. By March 2026, after feedback and discussions co-maintainer Sasha Levin helped steer, Greg partially rolled the clock back for the existing active trees.

6.6 and 6.1 now run through the end of 2027 instead of 2026. 6.12 and 6.18 push out to 2028 and 2027 respectively. The flip side landed squarely on the two oldest branches in this week's batch.

Both 5.10 and 5.15 hit end of life on December 31, 2026. About two months out from today. After that date, upstream stops shipping security fixes for them.

5.15 debuted in late October 2021, close enough to Halloween that kernel folks gave it the nickname "Trick or Treat." Two years on, it's still doing the heavy lifting as the base of Ubuntu 22.04 LTS, one of the largest installs on the planet. That's exactly why its December deadline generates real migration pressure.

5.10 has a lifeline, though. The Civil Infrastructure Platform maintains a 5.10 SLTS kernel until January 2031, which gives automotive, factory automation and industrial deployments a sanctioned route past the upstream cutoff. For everyone else running on 5.10, from RHEL 9 systems to a pile of edge and IoT boxes, the clock is genuinely running out.

Analysts at The New Stack have flagged this pattern repeatedly. The message is plain: projects still anchored on 5.10 or 5.15 should be planning their upgrade now, not after the deadline passes.

What to actually do

If you're on 5.10 or 5.15, treat the next two months as a planning window, not a panic. Migrate to 6.1 or 6.6 if you haven't already, or lean on the CIP SLTS path if you're locked into industrial hardware.

Those on 6.1 or 6.6 can breathe. Both stay healthy through the end of 2027, so there's no timing urgency. Apply this week's update for the security backports and get back to work.

Linux kernel 6.6.159 released

Linux kernel version 6.6.159 is now available:

Full source: https://cdn.kernel.org/pub/linux/kernel/v6.x/linux-6.6.159.tar.xz
Patch: https://cdn.kernel.org/pub/linux/kernel/v6.x/patch-6.6.159.xz
PGP Signature: https://cdn.kernel.org/pub/linux/kernel/v6.x/linux-6.6.159.tar.sign

You can view the summary of the changes at the following URL:
https://git.kernel.org/stable/ds/v6.6.159/v6.6.158

Linux kernel 6.1.190 released

Linux kernel version 6.1.190 is now available:

Full source: https://cdn.kernel.org/pub/linux/kernel/v6.x/linux-6.1.190.tar.xz
Patch: https://cdn.kernel.org/pub/linux/kernel/v6.x/patch-6.1.190.xz
PGP Signature: https://cdn.kernel.org/pub/linux/kernel/v6.x/linux-6.1.190.tar.sign

You can view the summary of the changes at the following URL:
https://git.kernel.org/stable/ds/v6.1.190/v6.1.189

Linux kernel 5.15.223 released

Linux kernel version 5.15.223 is now available:

Full source: https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.15.223.tar.xz
Patch: https://cdn.kernel.org/pub/linux/kernel/v5.x/patch-5.15.223.xz
PGP Signature: https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.15.223.tar.sign

You can view the summary of the changes at the following URL:
https://git.kernel.org/stable/ds/v5.15.223/v5.15.222

Linux kernel 5.10.272 released

Linux kernel version 5.10.272 is now available:

Full source: https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.10.272.tar.xz
Patch: https://cdn.kernel.org/pub/linux/kernel/v5.x/patch-5.10.272.xz
PGP Signature: https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.10.272.tar.sign

You can view the summary of the changes at the following URL:
https://git.kernel.org/stable/ds/v5.10.272/v5.10.271