USN-5497-2: Libjpeg6b vulnerabilities

USN-5497-1 fixed vulnerabilities in Libjpeg6b. This update provides the corresponding updates for Ubuntu 16.04 ESM. Original advisory details: It was discovered that Libjpeg6b was not properly performing bounds checks when compressing PPM and Targa image files. An attacker could possibly use this issue to cause a denial of service. (CVE-2018-11212) Chijin Zhou discovered that Libjpeg6b was incorrectly handling the EOF character in input data when generating JPEG files. An attacker could possibly use this issue to force the execution of a large loop, force excessive memory consumption, and cause a denial of service. (CVE-2018-11813) Sheng Shu and Dongdong She discovered that Libjpeg6b was not properly limiting the amount of memory being used when it was performing decompression or multi-pass compression operations. An attacker could possibly use this issue to force excessive memory consumption and cause a denial of service. (CVE-2020-14152)