14 DAY TRIAL // Ubuntu 15.04, Ubuntu 14.10, Ubuntu 14.04 LTS, and Ubuntu 12.04 LTS have been updated in order to fix a few OpenLDAP vulnerabilities that have been found.
OpenLDAP is the open source implementation of Lightweight Directory Access Protocol, and from the looks of it, OpenLDAP could have been made to crash if it received specially crafted network traffic.
"It was discovered that OpenLDAP incorrectly handled certain empty attribute lists in search requests. A remote attacker could use this issue to cause OpenLDAP to crash, resulting in a denial of service," the official notification reads.
This is just one of the issues that have been identified and corrected in Ubuntu OSes. For a more detailed description of the problems, you can see Canonical's security notification. Users have been advised to upgrade their systems as soon as possible.
In general, a standard system update will make all the necessary changes, and you don't have to restart the PC in order to complete the update as this is not a core component.
You can also use the terminal to update the system. Just enter these commands in a terminal near you:
sudo apt-get dist-upgrade