A Linux kernel security update has been released for Ubuntu Linux 20.04 LTS and 21.04.

USN-5046-1: Linux kernel vulnerabilities

=========================================================================
Ubuntu Security Notice USN-5046-1
August 18, 2021

linux, linux-aws, linux-azure, linux-gcp, linux-hwe-5.11, linux-oracle,
linux-raspi vulnerabilities
=========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 21.04
- Ubuntu 20.04 LTS

Summary:

Several security issues were fixed in the Linux kernel.

Software Description:
- linux: Linux kernel
- linux-aws: Linux kernel for Amazon Web Services (AWS) systems
- linux-azure: Linux kernel for Microsoft Azure Cloud systems
- linux-gcp: Linux kernel for Google Cloud Platform (GCP) systems
- linux-oracle: Linux kernel for Oracle Cloud systems
- linux-raspi: Linux kernel for Raspberry Pi (V8) systems
- linux-hwe-5.11: Linux hardware enablement (HWE) kernel

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-2021-3587)

Update instructions:

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

Ubuntu 21.04:
linux-image-5.11.0-1013-azure 5.11.0-1013.14
linux-image-5.11.0-1016-aws 5.11.0-1016.17
linux-image-5.11.0-1016-oracle 5.11.0-1016.17
linux-image-5.11.0-1016-raspi 5.11.0-1016.17
linux-image-5.11.0-1016-raspi-nolpae 5.11.0-1016.17
linux-image-5.11.0-1017-gcp 5.11.0-1017.19
linux-image-5.11.0-31-generic 5.11.0-31.33
linux-image-5.11.0-31-generic-64k 5.11.0-31.33
linux-image-5.11.0-31-generic-lpae 5.11.0-31.33
linux-image-5.11.0-31-lowlatency 5.11.0-31.33
linux-image-aws 5.11.0.1016.17
linux-image-azure 5.11.0.1013.14
linux-image-gcp 5.11.0.1017.17
linux-image-generic 5.11.0.31.33
linux-image-generic-64k 5.11.0.31.33
linux-image-generic-lpae 5.11.0.31.33
linux-image-gke 5.11.0.1017.17
linux-image-lowlatency 5.11.0.31.33
linux-image-oem-20.04 5.11.0.31.33
linux-image-oracle 5.11.0.1016.17
linux-image-raspi 5.11.0.1016.14
linux-image-raspi-nolpae 5.11.0.1016.14
linux-image-virtual 5.11.0.31.33

Ubuntu 20.04 LTS:
linux-image-5.11.0-27-generic 5.11.0-27.29~20.04.1
linux-image-5.11.0-27-generic-64k 5.11.0-27.29~20.04.1
linux-image-5.11.0-27-generic-lpae 5.11.0-27.29~20.04.1
linux-image-5.11.0-27-lowlatency 5.11.0-27.29~20.04.1
linux-image-generic-64k-hwe-20.04 5.11.0.27.29~20.04.11
linux-image-generic-hwe-20.04 5.11.0.27.29~20.04.11
linux-image-generic-lpae-hwe-20.04 5.11.0.27.29~20.04.11
linux-image-lowlatency-hwe-20.04 5.11.0.27.29~20.04.11
linux-image-virtual-hwe-20.04 5.11.0.27.29~20.04.11

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-5046-1
CVE-2020-26558, CVE-2021-0129, CVE-2021-28691, CVE-2021-3564,
CVE-2021-3573, CVE-2021-3587

Package Information:
  https://launchpad.net/ubuntu/+source/linux/5.11.0-31.33
  https://launchpad.net/ubuntu/+source/linux-aws/5.11.0-1016.17
  https://launchpad.net/ubuntu/+source/linux-azure/5.11.0-1013.14
  https://launchpad.net/ubuntu/+source/linux-gcp/5.11.0-1017.19
  https://launchpad.net/ubuntu/+source/linux-oracle/5.11.0-1016.17
  https://launchpad.net/ubuntu/+source/linux-raspi/5.11.0-1016.17
  https://launchpad.net/ubuntu/+source/linux-hwe-5.11/5.11.0-27.29~20.04.1