Ubuntu Security Notice 999-1 – Mike Roszkowski discovered that the Kerberos KDC did not correctly validate the contents of certain messages. If an authenticated remote attacker sent specially crafted TGS requests, the KDC service would crash, leading to a denial of service.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/94523/USN-999-1.txt
Source: https://packetstormsecurity.com/files/94523/Ubuntu-Security-Notice-999-1.html