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USN-3740-1: Linux kernel vulnerabilities

14 August 2018

Several security issues were fixed in the Linux kernel.



  • linux - Linux kernel
  • linux-aws - Linux kernel for Amazon Web Services (AWS) systems
  • linux-azure - Linux kernel for Microsoft Azure Cloud systems
  • linux-gcp - Linux kernel for Google Cloud Platform (GCP) systems
  • linux-kvm - Linux kernel for cloud environments
  • linux-oem - Linux kernel for OEM processors
  • linux-raspi2 - Linux kernel for Raspberry Pi 2


It was discovered that memory present in the L1 data cache of an Intel CPU
core may be exposed to a malicious process that is executing on the CPU
core. This vulnerability is also known as L1 Terminal Fault (L1TF). A local
attacker in a guest virtual machine could use this to expose sensitive
information (memory from other guests or the host OS). (CVE-2018-3646)

It was discovered that memory present in the L1 data cache of an Intel CPU
core may be exposed to a malicious process that is executing on the CPU
core. This vulnerability is also known as L1 Terminal Fault (L1TF). A local
attacker could use this to expose sensitive information (memory from the
kernel or other processes). (CVE-2018-3620)

Juha-Matti Tilli discovered that the IP implementation in the Linux kernel
performed algorithmically expensive operations in some situations when
handling incoming packet fragments. A remote attacker could use this to
cause a denial of service. (CVE-2018-5391)

Update instructions

The problem can be corrected by updating your system to the following package versions:

Ubuntu 18.04

Please note that the recommended mitigation for CVE-2018-3646 involves
updating processor microcode in addition to updating the kernel;
however, the kernel includes a fallback for processors that have not
received microcode updates.

After a standard system update you need to reboot your computer to make
all the necessary changes.

ATTENTION: Due to an unavoidable ABI change the kernel updates have
been given a new version number, which requires you to recompile and
reinstall all third party kernel modules you might have installed.
Unless you manually uninstalled the standard kernel metapackages
(e.g. linux-generic, linux-generic-lts-RELEASE, linux-virtual,
linux-powerpc), a standard system upgrade will automatically perform
this as well.

Related notices

  • USN-3742-1: linux-image-3.13.0-155-generic-lpae, linux-image-3.13.0-155-lowlatency, linux-image-3.13.0-155-powerpc-e500mc, linux, linux-image-3.13.0-155-generic, linux-image-3.13.0-155-powerpc-smp, linux-image-3.13.0-155-powerpc64-smp, linux-image-3.13.0-155-powerpc64-emb, linux-image-3.13.0-155-powerpc-e500, linux-image-extra-3.13.0-155-generic
  • USN-3742-2: linux-image-3.13.0-155-generic-lpae, linux-image-generic-lts-trusty, linux-image-generic-lpae-lts-trusty, linux-image-3.13.0-155-generic, linux-lts-trusty
  • USN-3823-1: linux-image-omap, linux-image-3.2.0-137-omap, linux, linux-image-powerpc-smp, linux-image-virtual, linux-image-highbank, linux-image-3.2.0-137-generic-pae, linux-image-3.2.0-137-powerpc64-smp, linux-image-3.2.0-137-generic, linux-image-3.2.0-137-powerpc-smp, linux-image-generic-pae, linux-image-3.2.0-137-highbank, linux-image-powerpc, linux-image-generic, linux-image-powerpc64-smp, linux-image-3.2.0-137-virtual
  • USN-3741-2: linux-image-4.4.0-133-powerpc64-emb, linux-image-extra-4.4.0-133-generic, linux-aws, linux-image-4.4.0-133-powerpc-e500mc, linux-image-4.4.0-133-lowlatency, linux-image-4.4.0-133-powerpc64-smp, linux-lts-xenial, linux-image-4.4.0-133-powerpc-smp, linux-image-4.4.0-133-generic-lpae, linux-image-4.4.0-1027-aws, linux-image-4.4.0-133-generic
  • USN-3741-1: linux-image-4.4.0-133-powerpc64-emb, linux-image-4.4.0-1065-aws, linux-image-extra-4.4.0-133-generic, linux-image-4.4.0-1094-raspi2, linux, linux-aws, linux-image-4.4.0-133-generic-lpae, linux-image-4.4.0-133-lowlatency, linux-image-4.4.0-133-powerpc-e500mc, linux-image-4.4.0-133-powerpc64-smp, linux-raspi2, linux-image-4.4.0-1031-kvm, linux-image-4.4.0-133-powerpc-smp, linux-kvm, linux-snapdragon, linux-image-4.4.0-1098-snapdragon, linux-image-4.4.0-133-generic
  • USN-3740-2: linux-image-unsigned-4.15.0-32-generic, linux-image-4.15.0-32-generic-lpae, linux-image-unsigned-4.15.0-32-lowlatency, linux-hwe, linux-image-unsigned-4.15.0-1021-azure, linux-image-4.15.0-32-generic, linux-gcp, linux-azure, linux-image-4.15.0-32-lowlatency, linux-image-4.15.0-1017-gcp
  • USN-3756-1: intel-microcode