A Linux kernel (Azure) security update has been released for Ubuntu Linux 14.04 LTS, 16.04 LTS, and 18.04 LTS.

[USN-6342-2] Linux kernel (Azure) vulnerabilities

==========================================================================
Ubuntu Security Notice USN-6342-2
September 08, 2023

linux-azure, linux-azure-4.15 vulnerabilities
==========================================================================

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

- Ubuntu 18.04 LTS (Available with Ubuntu Pro)
- Ubuntu 16.04 LTS (Available with Ubuntu Pro)
- Ubuntu 14.04 LTS (Available with Ubuntu Pro)

Summary:

Several security issues were fixed in the Linux kernel.

Software Description:
- linux-azure-4.15: Linux kernel for Microsoft Azure Cloud systems
- linux-azure: Linux kernel for Microsoft Azure Cloud systems

Details:

Tavis Ormandy discovered that some AMD processors did not properly handle
speculative execution of certain vector register instructions. A local
attacker could use this to expose sensitive information. (CVE-2023-20593)

Zheng Zhang discovered that the device-mapper implementation in the Linux
kernel did not properly handle locking during table_clear() operations. A
local attacker could use this to cause a denial of service (kernel
deadlock). (CVE-2023-2269)

It was discovered that a use-after-free vulnerability existed in the HFS+
file system implementation in the Linux kernel. A local attacker could
possibly use this to cause a denial of service (system crash).
(CVE-2023-2985)

It was discovered that the DVB Core driver in the Linux kernel did not
properly handle locking events in certain situations. A local attacker
could use this to cause a denial of service (kernel deadlock).
(CVE-2023-31084)

It was discovered that the Quick Fair Queueing network scheduler
implementation in the Linux kernel contained an out-of-bounds write
vulnerability. A local attacker could use this to cause a denial of service
(system crash) or possibly execute arbitrary code. (CVE-2023-3611)

It was discovered that the network packet classifier with
netfilter/firewall marks implementation in the Linux kernel did not
properly handle reference counting, 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-2023-3776)

Update instructions:

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

Ubuntu 18.04 LTS (Available with Ubuntu Pro):
linux-image-4.15.0-1169-azure 4.15.0-1169.184
linux-image-azure-lts-18.04 4.15.0.1169.137

Ubuntu 16.04 LTS (Available with Ubuntu Pro):
linux-image-4.15.0-1169-azure 4.15.0-1169.184~16.04.1
linux-image-azure 4.15.0.1169.153

Ubuntu 14.04 LTS (Available with Ubuntu Pro):
linux-image-4.15.0-1169-azure 4.15.0-1169.184~14.04.1
linux-image-azure 4.15.0.1169.135

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-6342-2
https://ubuntu.com/security/notices/USN-6342-1
CVE-2023-20593, CVE-2023-2269, CVE-2023-2985, CVE-2023-31084,
CVE-2023-3611, CVE-2023-3776