Ubuntu Security Notice 529-1 – It was discovered that Tk could be made to overrun a buffer when loading certain images. If a user were tricked into opening a specially crafted GIF image, remote attackers could cause a denial of service or execute arbitrary code with user privileges.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/60032/USN-529-1.txt
Source: https://packetstormsecurity.com/files/60032/Ubuntu-Security-Notice-529-1.html