Ubuntu Security Notice 3221-2 – USN-3221-1 fixed vulnerabilities in the Linux kernel for Ubuntu 16.10. This update provides the corresponding updates for the Linux Hardware Enablement kernel from Ubuntu 16.10 for Ubuntu 16.04 LTS. Alexander Popov discovered that the N_HDLC line discipline implementation in the Linux kernel contained a double-free vulnerability. A local attacker could use this to cause a denial of service or possibly gain administrative privileges. Various other issues were also addressed.