This update is based on upstream 5.4.6 and fixes various potential security issues related to buffer overflows, double frees, NUll pointer dereferences, improper / missing input validations and so on. It also adds other bugfixes all over the kernel.
Other fixes added in this update:
WireGuard has been updated to 0.0.20191219.
For other fixes in this update, see the referenced changelogs.