A python-apt security update has been released for Ubuntu Linux 14.04 ESM and 12.04 ESM.

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Ubuntu Security Notice USN-4247-3
January 23, 2020

python-apt vulnerabilities
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 14.04 ESM
- Ubuntu 12.04 ESM

Summary:

Several security issues were fixed in python-apt.

Software Description:
- python-apt: Python interface to libapt-pkg

Details:

USN-4247-1 fixed several vulnerabilities in python-apt. This update
provides the corresponding updates for Ubuntu 12.04 ESM and Ubuntu 14.04 ESM.

Original advisory details:

It was discovered that python-apt would still use MD5 hashes to validate
certain downloaded packages. If a remote attacker were able to perform a
man-in-the-middle attack, this flaw could potentially be used to install
altered packages. (CVE-2019-15795)

It was discovered that python-apt could install packages from untrusted
repositories, contrary to expectations. (CVE-2019-15796)

Update instructions:

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

Ubuntu 14.04 ESM:
python-apt 0.9.3.5ubuntu3+esm2
python3-apt 0.9.3.5ubuntu3+esm2

Ubuntu 12.04 ESM:
python-apt 0.8.3ubuntu7.5
python3-apt 0.8.3ubuntu7.5

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

References:
  https://usn.ubuntu.com/4247-3
  https://usn.ubuntu.com/4247-1
CVE-2019-15795, CVE-2019-15796