LSN-0071-1: Kernel Live Patch Security Notice

10 September 2020

Linux kernel vulnerabilities

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

  • Ubuntu 16.04 LTS
  • Ubuntu 18.04 LTS
  • Ubuntu 20.04 LTS

Summary

A security issue was fixed in the 4.15 kernel. This issue affects the 5.4 kernel as well, but a livepatch is not yet available. While work is continuing to develop livepatches for all affected kernels, due to the severity of the issue, we are releasing patches as they become ready.

Software Description

  • linux - Linux kernel
  • linux-aws - Linux kernel for Amazon Web Services (AWS) systems
  • linux-oem - Linux kernel for OEM systems

Details

Or Cohen discovered that the AF_PACKET implementation in the Linux kernel did not properly perform bounds checking in some situations. A local attacker could use this to cause a denial of service (system crash) or possibly execute arbitrary code. (CVE-2020-14386)

Update instructions

The problem can be corrected by updating your kernel livepatch to the following versions:

Ubuntu 18.04 LTS
aws - 71.1
generic - 71.1
lowlatency - 71.1
oem - 71.1

A mitigation is available if your kernel is affected, did not yet receive a livepatch, and rebooting into the most recently released kernel is not practical. If your system does not require the use of unprivileged user namespaces, you may disable them and mitigate the problem using the following command:

sudo sysctl kernel.unprivileged_userns_clone=0

Support Information

Kernels older than the levels listed below do not receive livepatch updates. If you are running a kernel version earlier than the one listed below, please upgrade your kernel as soon as possible.

Ubuntu 18.04 LTS
linux-aws - 4.15.0-1054
linux-oem - 4.15.0-1063
linux - 4.15.0-69
Ubuntu 16.04 LTS
linux-azure - 4.15.0-1063

References