A Sudo security update has been released for Ubuntu Linux 19.10, 18.04 LTS, and 16.04 LTS.

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Ubuntu Security Notice USN-4263-1
February 03, 2020

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

- Ubuntu 19.10
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS

Summary:

Sudo could allow unintended access to the administrator account.

Software Description:
- sudo: Provide limited super user privileges to specific users

Details:

Joe Vennix discovered that Sudo incorrectly handled memory operations when
the pwfeedback option is enabled. A local attacker could possibly use this
issue to obtain unintended access to the administrator account.

Update instructions:

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

Ubuntu 19.10:
sudo 1.8.27-1ubuntu4.1
sudo-ldap 1.8.27-1ubuntu4.1

Ubuntu 18.04 LTS:
sudo 1.8.21p2-3ubuntu1.2
sudo-ldap 1.8.21p2-3ubuntu1.2

Ubuntu 16.04 LTS:
sudo 1.8.16-0ubuntu1.9
sudo-ldap 1.8.16-0ubuntu1.9

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

References:
  https://usn.ubuntu.com/4263-1
CVE-2019-18634

Package Information:
  https://launchpad.net/ubuntu/+source/sudo/1.8.27-1ubuntu4.1
  https://launchpad.net/ubuntu/+source/sudo/1.8.21p2-3ubuntu1.2
  https://launchpad.net/ubuntu/+source/sudo/1.8.16-0ubuntu1.9