A Linux kernel security update has been released for Ubuntu Linux 20.04 LTS.

USN-5050-1: Linux kernel vulnerabilities

=========================================================================
Ubuntu Security Notice USN-5050-1
August 24, 2021

linux-aws-5.8, linux-azure-5.8, linux-gcp-5.8, linux-oracle-5.8
vulnerabilities
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 20.04 LTS

Summary:

Several security issues were fixed in the Linux kernel.

Software Description:
- linux-aws-5.8: Linux kernel for Amazon Web Services (AWS) systems
- linux-azure-5.8: Linux kernel for Microsoft Azure cloud systems
- linux-gcp-5.8: Linux kernel for Google Cloud Platform (GCP) systems
- linux-oracle-5.8: Linux kernel for Oracle Cloud systems

Details:

It was discovered that the bluetooth subsystem in the Linux kernel did not
properly perform access control. An authenticated attacker could possibly
use this to expose sensitive information. (CVE-2020-26558, CVE-2021-0129)

Michael Brown discovered that the Xen netback driver in the Linux kernel
did not properly handle malformed packets from a network PV frontend,
leading to a use-after-free vulnerability. An attacker in a guest VM could
use this to cause a denial of service or possibly execute arbitrary code.
(CVE-2021-28691)

It was discovered that the bluetooth subsystem in the Linux kernel did not
properly handle HCI device initialization failure, leading to a double-free
vulnerability. An attacker could use this to cause a denial of service or
possibly execute arbitrary code. (CVE-2021-3564)

It was discovered that the bluetooth subsystem in the Linux kernel did not
properly handle HCI device detach events, leading to a use-after-free
vulnerability. An attacker could use this to cause a denial of service or
possibly execute arbitrary code. (CVE-2021-3573)

It was discovered that the NFC implementation in the Linux kernel did not
properly handle failed connect events leading to a NULL pointer
dereference. A local attacker could use this to cause a denial of service.
(CVE-2021-38208)

Update instructions:

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

Ubuntu 20.04 LTS:
linux-image-5.8.0-1038-oracle 5.8.0-1038.39~20.04.1
linux-image-5.8.0-1039-gcp 5.8.0-1039.41
linux-image-5.8.0-1040-azure 5.8.0-1040.43~20.04.1
linux-image-5.8.0-1042-aws 5.8.0-1042.44~20.04.1
linux-image-aws 5.8.0.1042.44~20.04.14
linux-image-azure 5.8.0.1040.43~20.04.12
linux-image-gcp 5.8.0.1039.14
linux-image-oracle 5.8.0.1038.39~20.04.14

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.

References:
  https://ubuntu.com/security/notices/USN-5050-1
CVE-2020-26558, CVE-2021-0129, CVE-2021-28691, CVE-2021-3564,
CVE-2021-3573, CVE-2021-38208

Package Information:
  https://launchpad.net/ubuntu/+source/linux-aws-5.8/5.8.0-1042.44~20.04.1
  https://launchpad.net/ubuntu/+source/linux-azure-5.8/5.8.0-1040.43~20.04.1
  https://launchpad.net/ubuntu/+source/linux-gcp-5.8/5.8.0-1039.41
  https://launchpad.net/ubuntu/+source/linux-oracle-5.8/5.8.0-1038.39~20.04.1