The following updates has been released for Ubuntu Linux:

USN-4106-1: NLTK vulnerability
USN-4107-1: GIFLIB vulnerabilities

USN-4106-1: NLTK vulnerability

==========================================================================
Ubuntu Security Notice USN-4106-1
August 20, 2019

NLTK vulnerability
==========================================================================

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

- Ubuntu 19.04
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS

Summary:

NLTK could be made to overwrite files.

Software Description:
- nltk: Python libraries for natural language processing

Details:

Mike Salvatore discovered that NLTK mishandled crafted ZIP archives during
extraction. A remote attacker could use this vulnerability to write
arbitrary files to the filesystem

Update instructions:

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

Ubuntu 19.04:
python-nltk 3.4-1ubuntu0.1
python3-nltk 3.4-1ubuntu0.1

Ubuntu 18.04 LTS:
python-nltk 3.2.5-1ubuntu0.1
python3-nltk 3.2.5-1ubuntu0.1

Ubuntu 16.04 LTS:
python-nltk 3.1-1ubuntu0.1
python3-nltk 3.1-1ubuntu0.1

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

References:
https://usn.ubuntu.com/4106-1
CVE-2019-14751

Package Information:
https://launchpad.net/ubuntu/+source/nltk/3.4-1ubuntu0.1
https://launchpad.net/ubuntu/+source/nltk/3.2.5-1ubuntu0.1
https://launchpad.net/ubuntu/+source/nltk/3.1-1ubuntu0.1

USN-4107-1: GIFLIB vulnerabilities

=========================================================================
Ubuntu Security Notice USN-4107-1
August 20, 2019

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

- Ubuntu 19.04
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS

Summary:

Several security issues were fixed in GIFLIB.

Software Description:
- giflib: library for GIF images (utilities)

Details:

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)

Update instructions:

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

Ubuntu 19.04:
giflib-tools 5.1.4-3ubuntu0.1
libgif7 5.1.4-3ubuntu0.1

Ubuntu 18.04 LTS:
giflib-tools 5.1.4-2ubuntu0.1
libgif7 5.1.4-2ubuntu0.1

Ubuntu 16.04 LTS:
giflib-tools 5.1.4-0.3~16.04.1
libgif7 5.1.4-0.3~16.04.1

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

References:
https://usn.ubuntu.com/4107-1
CVE-2016-3977, CVE-2018-11490, CVE-2019-15133

Package Information:
https://launchpad.net/ubuntu/+source/giflib/5.1.4-3ubuntu0.1
https://launchpad.net/ubuntu/+source/giflib/5.1.4-2ubuntu0.1
https://launchpad.net/ubuntu/+source/giflib/5.1.4-0.3~16.04.1