Ubuntu Security Notice 538-1 – It was discovered that libpng did not properly perform bounds checking and comparisons in certain operations. An attacker could send a specially crafted PNG image and cause a denial of service in applications linked against libpng.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/60443/USN-538-1.txt
Source: https://packetstormsecurity.com/files/60443/Ubuntu-Security-Notice-538-1.html