1. Ubuntu Security Notices
  2. USN-3836-1

USN-3836-1: Linux kernel vulnerabilities

Publication date

3 December 2018

Overview

Several security issues were fixed in the Linux kernel.

Releases

Packages

  • linux - Linux kernel
  • linux-gcp - Linux kernel for Google Cloud Platform (GCP) systems
  • linux-kvm - Linux kernel for cloud environments
  • linux-raspi2 - Linux kernel for Raspberry Pi 2

Details

Jann Horn discovered that the Linux kernel mishandles mapping UID or GID
ranges inside nested user namespaces in some situations. A local attacker
could use this to bypass access controls on resources outside the
namespace. (CVE-2018-18955)

Philipp Wendler discovered that the overlayfs implementation in the Linux
kernel did not properly verify the directory contents permissions from
within a unprivileged user namespace. A local attacker could use this to
expose sensitive information (protected file names). (CVE-2018-6559)

Jann Horn discovered that the Linux kernel mishandles mapping UID or GID
ranges inside nested user namespaces in some situations. A local attacker
could use this to bypass access controls on resources outside the
namespace. (CVE-2018-18955)

Philipp Wendler discovered that the overlayfs implementation in the Linux
kernel did not properly verify the directory contents permissions from
within a unprivileged user namespace. A local attacker could use this to
expose sensitive information (protected file names). (CVE-2018-6559)

Update instructions

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

Learn more about how to get the fixes.

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.

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

Ubuntu Release Package Version
18.04 bionic linux-image-4.15.0-1027-kvm –  4.15.0-1027.27
linux-image-4.15.0-1029-raspi2 –  4.15.0-1029.31
linux-image-4.15.0-42-generic –  4.15.0-42.45
linux-image-4.15.0-42-generic-lpae –  4.15.0-42.45
linux-image-4.15.0-42-lowlatency –  4.15.0-42.45
linux-image-4.15.0-42-snapdragon –  4.15.0-42.45

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References

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