Ubuntu Security Notice 550-3 – USN-550-1 fixed vulnerabilities in Cairo. A bug in font glyph rendering was uncovered as a result of the new memory allocation routines. In certain situations, fonts containing characters with no width or height would not render any more. This update fixes the problem. Peter Valchev discovered that Cairo did not correctly decode PNG image data. By tricking a user or automated system into processing a specially crafted PNG with Cairo, a remote attacker could execute arbitrary code with user privileges.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/61795/USN-550-3.txt
Source: https://packetstormsecurity.com/files/61795/Ubuntu-Security-Notice-550-3.html