A Linux kernel security update has been released for Ubuntu Linux 18.04 LTS and 20.04 LTS.

[USN-6387-2] Linux kernel vulnerabilities

==========================================================================
Ubuntu Security Notice USN-6387-2
September 26, 2023

linux-bluefield, linux-raspi, linux-raspi-5.4 vulnerabilities
==========================================================================

A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS (Available with Ubuntu Pro)

Summary:

Several security issues were fixed in the Linux kernel.

Software Description:
- linux-bluefield: Linux kernel for NVIDIA BlueField platforms
- linux-raspi: Linux kernel for Raspberry Pi systems
- linux-raspi-5.4: Linux kernel for Raspberry Pi systems

Details:

Jana Hofmann, Emanuele Vannacci, Cedric Fournet, Boris Kopf, and Oleksii
Oleksenko discovered that some AMD processors could leak stale data from
division operations in certain situations. A local attacker could possibly
use this to expose sensitive information. (CVE-2023-20588)

It was discovered that the bluetooth subsystem in the Linux kernel did not
properly handle L2CAP socket release, leading to a use-after-free
vulnerability. A local attacker could use this to cause a denial of service
(system crash) or possibly execute arbitrary code. (CVE-2023-40283)

It was discovered that some network classifier implementations in the Linux
kernel contained use-after-free vulnerabilities. A local attacker could use
this to cause a denial of service (system crash) or possibly execute
arbitrary code. (CVE-2023-4128)

Update instructions:

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

Ubuntu 20.04 LTS:
linux-image-5.4.0-1071-bluefield 5.4.0-1071.77
linux-image-5.4.0-1094-raspi 5.4.0-1094.105
linux-image-bluefield 5.4.0.1071.66
linux-image-raspi 5.4.0.1094.124
linux-image-raspi2 5.4.0.1094.124

Ubuntu 18.04 LTS (Available with Ubuntu Pro):
linux-image-5.4.0-1094-raspi 5.4.0-1094.105~18.04.1
linux-image-raspi-hwe-18.04 5.4.0.1094.91

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-6387-2
https://ubuntu.com/security/notices/USN-6387-1
CVE-2023-20588, CVE-2023-40283, CVE-2023-4128

Package Information:
https://launchpad.net/ubuntu/+source/linux-bluefield/5.4.0-1071.77
https://launchpad.net/ubuntu/+source/linux-raspi/5.4.0-1094.105