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Security Advisory

USN-4318-1: Linux kernel vulnerabilities

USN-4318-1: Linux kernel vulnerabilities




Canonical Ubuntu

Versions Affected

  • Canonical Ubuntu 16.04


Al Viro discovered that the vfs layer in the Linux kernel contained a use- after-free vulnerability. A local attacker could use this to cause a denial of service (system crash) or possibly expose sensitive information (kernel memory). (CVE-2020-8428)

Gustavo Romero and Paul Mackerras discovered that the KVM implementation in the Linux kernel for PowerPC processors did not properly keep guest state separate from host state. A local attacker in a KVM guest could use this to cause a denial of service (host system crash). (CVE-2020-8834)

Shijie Luo discovered that the ext4 file system implementation in the Linux kernel did not properly check for a too-large journal size. An attacker could use this to construct a malicious ext4 image that, when mounted, could cause a denial of service (soft lockup). (CVE-2020-8992)

CVEs contained in this USN include: CVE-2020-8428, CVE-2020-8834, CVE-2020-8992.

Affected Cloud Foundry Products and Versions

Severity is medium unless otherwise noted.

  • Xenial Stemcells
    • 170.x versions prior to 170.215
    • 250.x versions prior to 250.196
    • 315.x versions prior to 315.179
    • 456.x versions prior to 456.108
    • 621.x versions prior to 621.69
    • All other stemcells not listed.


Users of affected products are strongly encouraged to follow the mitigations below. The Cloud Foundry project recommends upgrading the following releases:

  • Xenial Stemcells
    • Upgrade 170.x versions to 170.215 or greater
    • Upgrade 250.x versions to 250.196 or greater
    • Upgrade 315.x versions to 315.179 or greater
    • Upgrade 456.x versions to 456.108 or greater
    • Upgrade 621.x versions to 621.69 or greater
    • All other stemcells should be upgraded to the latest version available on


2020-04-06: Initial vulnerability report published.

Cloud Foundry Foundation Security Team Profile Image

Cloud Foundry Foundation Security Team, AUTHOR