Ubuntu Security Notice 2491-1 – Andy Lutomirski discovered that the Linux kernel does not properly handle faults associated with the Stack Segment (SS) register in the x86 architecture. A local attacker could exploit this flaw to gain administrative privileges. Lars Bull reported a race condition in the PIT (programmable interrupt timer) emulation in the KVM (Kernel Virtual Machine) subsystem of the Linux kernel. A local guest user with access to PIT i/o ports could exploit this flaw to cause a denial of service (crash) on the host. Various other issues were also addressed.