We’re able to quickly and safely ship the latest Linux kernel LTS point releases on devices with GKI (Generic Kernel Image) support including the 6th and 7th generation Pixel phones. At the time of writing on 2023-11-06, GrapheneOS is using the latest Linux 5.10 GKI LTS release (5.10.199) for 6th and 7th generation Pixel phones. The stock Pixel OS is on Linux 5.10.157 from 2022-12-02 with a small number of additional patches backported. This means GrapheneOS provides hundreds of relevant kernel patches including many security patches not yet included in the stock OS. It’s possible for us to stay several months ahead due to their approach of moving to new LTS releases only in quarterly releases after a long freeze and testing process.

From: https://grapheneos.org/features#more-complete-patching

Edit: GrapheneOS ships kernel 6.12.73 (two minor versions behind but it’s an LTS branch that gets constant backported security fixes) as of this month and gets LTS point releases out faster than stock Pixel OS. They’re also the only Android OS shipping full security preview patches, months before public disclosure. “Not the latest mainline kernel” and “less secure” are different things.