Several security issues were fixed in PolicyKit.
Tavis Ormandy discovered that PolicyKit incorrectly handled certain invalid object paths. A local attacker could possibly use this issue to cause PolicyKit to crash, resulting in a denial of service. This issue only affected Ubuntu 14.04 LTS. (CVE-2015-3218)
16 July 2018
A security issue affects these releases of Ubuntu and its derivatives:
Several security issues were fixed in PolicyKit.
Tavis Ormandy discovered that PolicyKit incorrectly handled certain invalid object paths. A local attacker could possibly use this issue to cause PolicyKit to crash, resulting in a denial of service. This issue only affected Ubuntu 14.04 LTS. (CVE-2015-3218)
It was discovered that PolicyKit incorrectly handled certain duplicate action IDs. A local attacker could use this issue to cause PolicyKit to crash, resulting in a denial of service, or possibly escalate privileges. This issue only affected Ubuntu 14.04 LTS. (CVE-2015-3255)
Tavis Ormandy discovered that PolicyKit incorrectly handled duplicate cookie values. A local attacker could use this issue to cause PolicyKit to crash, resulting in a denial of service, or possibly escalate privileges. This issue only affected Ubuntu 14.04 LTS. (CVE-2015-4625)
Matthias Gerstner discovered that PolicyKit incorrectly checked users. A local attacker could possibly use this issue to cause authentication dialogs to show up for other users, leading to a denial of service or an information leak. (CVE-2018-1116)
The problem can be corrected by updating your system to the following package versions:
To update your system, please follow these instructions: https://wiki.ubuntu.com/Security/Upgrades.
After a standard system update you need to reboot your computer to make all the necessary changes.