Microsoft has already rolled back the kernel in WSL2 while issues are debugged

The pre-release version had been bumped to a 6.6 kernel, but there are issues to rectify before it's ready for prime time.

What you need to know

• Recently, Microsoft announced that the kernel in WSL2 would finally be bumped to a more modern version, and was pushed to a pre-release version. 
• The new kernel, 6.6.36.3 has now been rolled back to the much older 5.15.153.1-2 while issues are debugged. 
• The issues could relate to iptables, which are required for popular tool, Docker. 

Recently, Microsoft announced it was finally going to bump the old kernel used in the Windows Subsystem for Linux (WSL) on WSL2 to something more modern. That hasn't happened on the stable release yet, and it's a good job. 

In the latest pre-release candidate of WSL2, the kernel has been rolled back from the newer 6.6.36.3 to the previously used 5.15.153.1-2 while issues are debugged. 

Here's the full changelog for WSL2 2.3.17 which is available to download now from GitHub. 

• Revert Linux kernel to 5.15.153.1-2 while issues are being debugged
• Fix race condition when WSL2 distribution is stopped
• Use a format attribute to catch printf format errors compile time
• Fix segfault in init when boot.initPath doesn't exist
• Add default Hyper-V firewall rules to allow inbound mDNS traffic
• Update Windows SDK to version 26100
• Update Microsoft.Windows.ImplementationLibrary to version 1.0.240803.1

The changelog isn't specific to what the issues are, but there are potential signs it could relate to iptables. This issue highlighted recently focuses on the feature, and it's particularly important since Docker, of note, relies on iptables. 

One possible explanation from a WSL Community Telegram group I'm part of suggests that because some Linux distros are moving to nftables in place of iptables, though the kernel itself hasn't dropped support for the latter. 

In any case, this doesn't affect the stable release of WSL2 right now, so if you're using that, then it's business as usual. If you're on the pre-release version, and you have been having troubles, then you'll probably want to hit the GitHub page and grab the latest release.