Affecting both the Linux 4.15 kernel used in Ubuntu 18.04 LTS (Bionic Beaver) and Ubuntu 16.04.6 LTS (Xenial Xerus) systems, the new security patch fixed an improperly implemented Spectre mitigation in the ptrace susbsystem (CVE-2019-15902), which could allow a local attacker to expose sensitive information. It also addresses a buffer overread (CVE-2019-15918) discovered that the SMB networking file system implementation, which could allow an attacker to expose sensitive information (kernel memory), two flaws (CVE-2019-15117 and CVE-2019-15118) discovered in the USB audio driver that may allow a physically proximate attacker to crash the system, and a flaw (CVE-2019-14821) in the KVM hypervisor implementation that let a local attacker to crash the system.