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Security Advisory

USN-3836-2: Linux kernel (HWE) vulnerabilities

USN-3836-2: Linux kernel (HWE) vulnerabilities




Canonical Ubuntu

Versions Affected

  • Canonical Ubuntu 16.04


USN-3836-1 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.

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)

CVEs contained in this USN include: CVE-2018-18955, CVE-2018-6559

Affected Cloud Foundry Products and Versions

Severity is medium unless otherwise noted.

  • Cloud Foundry BOSH xenial-stemcells are vulnerable, including:
    • 170.x versions prior to 170.12
    • 97.x versions prior to 97.39
    • All other stemcells not listed.


Users of affected products are strongly encouraged to follow one of the mitigations below:

  • The Cloud Foundry project recommends upgrading the following BOSH xenial-stemcells:
    • Upgrade 170.x versions to 170.12
    • Upgrade 97.x versions to 97.39
    • All other stemcells should be upgraded to the latest version available on


Cloud Foundry Foundation Security Team Profile Image

Cloud Foundry Foundation Security Team, AUTHOR