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

[USN-6329-1] Linux kernel vulnerabilities

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Ubuntu Security Notice USN-6329-1
August 31, 2023

linux-gcp-5.4, linux-oracle-5.4 vulnerabilities
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 18.04 LTS (Available with Ubuntu Pro)

Summary:

Several security issues were fixed in the Linux kernel.

Software Description:
- linux-gcp-5.4: Linux kernel for Google Cloud Platform (GCP) systems
- linux-oracle-5.4: Linux kernel for Oracle Cloud systems

Details:

Daniel Moghimi discovered that some Intel(R) Processors did not properly
clear microarchitectural state after speculative execution of various
instructions. A local unprivileged user could use this to obtain to
sensitive information. (CVE-2022-40982)

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)

It was discovered that the universal 32bit network packet classifier
implementation in the Linux kernel did not properly perform reference
counting in some situations, 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-2023-3609)

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-5.4.0-1107-oracle 5.4.0-1107.116~18.04.1
linux-image-5.4.0-1111-gcp 5.4.0-1111.120~18.04.1
linux-image-gcp 5.4.0.1111.87
linux-image-oracle 5.4.0.1107.116~18.04.79

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-6329-1
CVE-2022-40982, CVE-2023-20593, CVE-2023-3609, CVE-2023-3611,
CVE-2023-3776