USN-3732-2: Linux kernel (HWE) vulnerability

6 August 2018

linux-hwe, linux-azure, linux-gcp vulnerability

A security issue affects these releases of Ubuntu and its derivatives:

  • Ubuntu 16.04 LTS


The system could be made unavailable if it received specially crafted network traffic.

Software Description

  • linux-azure - Linux kernel for Microsoft Azure Cloud systems
  • linux-gcp - Linux kernel for Google Cloud Platform (GCP) systems
  • linux-hwe - Linux hardware enablement (HWE) kernel


USN-3732-1 fixed vulnerabilities in the Linux kernel for Ubuntu 18.04 LTS. This update provides the corresponding updates for the Linux Hardware Enablement (HWE) kernel from Ubuntu 18.04 LTS for Ubuntu 16.04 LTS.

Juha-Matti Tilli discovered that the TCP implementation in the Linux kernel performed algorithmically expensive operations in some situations when handling incoming packets. A remote attacker could use this to cause a denial of service.

Update instructions

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

Ubuntu 16.04 LTS
linux-image-4.15.0-1015-gcp - 4.15.0-1015.15~16.04.1
linux-image-4.15.0-1019-azure - 4.15.0-1019.19~16.04.1
linux-image-4.15.0-30-generic - 4.15.0-30.32~16.04.1
linux-image-4.15.0-30-generic-lpae - 4.15.0-30.32~16.04.1
linux-image-4.15.0-30-lowlatency - 4.15.0-30.32~16.04.1
linux-image-azure -
linux-image-gcp -
linux-image-generic-hwe-16.04 -
linux-image-generic-lpae-hwe-16.04 -
linux-image-gke -
linux-image-lowlatency-hwe-16.04 -

To update your system, please follow these instructions:

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.