Ubuntu 18.04 & 16.04 USN-6555-2 critical: X.Org X Server exploits

A security issue affects these releases of Ubuntu and its derivatives: - Ubuntu 18.04 LTS (Available with Ubuntu Pro) - Ubuntu 16.04 LTS (Available with Ubuntu Pro) Summary: Several security issues were fixed in X.Org X Server. Software Description: - xorg-server: X.Org X11 server Details: USN-6555-1 fixed several vulnerabilities in X.Org. This update provides the corresponding update for Ubuntu 16.04 LTS and Ubuntu 18.04 LTS. Original advisory details: Jan-Niklas Sohn discovered that the X.Org X Server incorrectly handled XKB button actions. An attacker could possibly use this issue to cause the X Server to crash, execute arbitrary code, or escalate privileges. (CVE-2023-6377) Jan-Niklas Sohn discovered that the X.Org X Server incorrectly handled memory when processing the RRChangeOutputProperty and RRChangeProviderProperty APIs. An attacker could possibly use this issue to cause the X Server to crash, or obtain sensitive information. (CVE-2023-6478)