Ubuntu Security Notice 2978-1 – David Matlack discovered that the Kernel-based Virtual Machine (KVM) implementation in the Linux kernel did not properly restrict variable Memory Type Range Registers (MTRR) in KVM guests. A privileged user in a guest VM could use this to cause a denial of service (system crash) in the host, expose sensitive information from the host, or possibly gain administrative privileges in the host. Philip Pettersson discovered that the Linux kernel’s ASN.1 DER decoder did not properly process certificate files with tags of indefinite length. A local unprivileged attacker could use this to cause a denial of service (system crash) or possibly execute arbitrary code with administrative privileges. Various other issues were also addressed.