Several security issues were fixed in zlib
It was discovered that zlib incorrectly handled pointer arithmetic. An attacker could use this issue to cause zlib to crash, resulting in a denial of service, or possibly execute arbitrary code. (CVE-2016-9840, CVE-2016-9841)
22 January 2020
A security issue affects these releases of Ubuntu and its derivatives:
Several security issues were fixed in zlib
It was discovered that zlib incorrectly handled pointer arithmetic. An attacker could use this issue to cause zlib to crash, resulting in a denial of service, or possibly execute arbitrary code. (CVE-2016-9840, CVE-2016-9841)
It was discovered that zlib incorrectly handled vectors involving left shifts of negative integers. An attacker could use this issue to cause zlib to crash, resulting in a denial of service, or possibly execute arbitrary code. (CVE-2016-9842)
It was discovered that zlib incorrectly handled vectors involving big-endian CRC calculation. An attacker could use this issue to cause zlib to crash, resulting in a denial of service, or possibly execute arbitrary code. (CVE-2016-9843)
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.