Three security vulnerabilities are patched in this new Linux kernel update for the latest Ubuntu 20.04 LTS (Focal Fossa) release, which was launched by Canonical on April 23rd, 2020. A first kernel security update was released just a week after its official launch. This new Linux kernel update fixes a flaw (CVE-2019-19377) discovered in the Btrfs file system implementation, which incorrectly detected blocks marked as dirty in certain situations, allowing an attacker to cause a denial of service (system crash) using a specially crafted file system image.