A zlib security update has been released for Ubuntu Linux 16.04 LTS to address several security issues.

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Ubuntu Security Notice USN-4246-1
January 22, 2020

zlib vulnerabilities
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 16.04 LTS

Summary:

Several security issues were fixed in zlib

Software Description:
- zlib: Lossless data-compression library

Details:

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)

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 16.04 LTS:
lib32z1 1:1.2.8.dfsg-2ubuntu4.3
lib64z1 1:1.2.8.dfsg-2ubuntu4.3
libn32z1 1:1.2.8.dfsg-2ubuntu4.3
libx32z1 1:1.2.8.dfsg-2ubuntu4.3
zlib1g 1:1.2.8.dfsg-2ubuntu4.3

In general, a standard system update will make all the necessary changes.

References:
  https://usn.ubuntu.com/4246-1
CVE-2016-9840, CVE-2016-9841, CVE-2016-9842, CVE-2016-9843

Package Information:
  https://launchpad.net/ubuntu/+source/zlib/1:1.2.8.dfsg-2ubuntu4.3