Several security issues were fixed in GIFLIB.
It was discovered that GIFLIB incorrectly handled certain GIF files. An attacker could possibly use this issue to cause a denial of service. This issue only affected Ubuntu 18.04 LTS. (CVE-2016-3977)
20 August 2019
A security issue affects these releases of Ubuntu and its derivatives:
Several security issues were fixed in GIFLIB.
It was discovered that GIFLIB incorrectly handled certain GIF files. An attacker could possibly use this issue to cause a denial of service. This issue only affected Ubuntu 18.04 LTS. (CVE-2016-3977)
It was discovered that GIFLIB incorrectly handled certain GIF files. An attacker could possibly use this issue to cause a denial of service. (CVE-2018-11490, CVE-2019-15133)
The problem can be corrected by updating your system to the following package versions:
To update your system, please follow these instructions: https://wiki.ubuntu.com/Security/Upgrades.
In general, a standard system update will make all the necessary changes.