A Linux kernel security update has been released for Ubuntu Linux 18.04 LTS and 20.04 LTS to address several security issues.

USN-5830-1: Linux kernel vulnerabilities

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Ubuntu Security Notice USN-5830-1
January 27, 2023

linux-azure, linux-azure-5.4, linux-raspi2 vulnerabilities
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS

Summary:

Several security issues were fixed in the Linux kernel.

Software Description:
- linux-azure: Linux kernel for Microsoft Azure Cloud systems
- linux-azure-5.4: Linux kernel for Microsoft Azure cloud systems
- linux-raspi2: Linux kernel for Raspberry Pi systems

Details:

It was discovered that the NFSD implementation in the Linux kernel did not
properly handle some RPC messages, leading to a buffer overflow. A remote
attacker could use this to cause a denial of service (system crash) or
possibly execute arbitrary code. (CVE-2022-43945)

Tamás Koczka discovered that the Bluetooth L2CAP handshake implementation
in the Linux kernel contained multiple use-after-free vulnerabilities. A
physically proximate attacker could use this to cause a denial of service
(system crash) or possibly execute arbitrary code. (CVE-2022-42896)

It was discovered that the Xen netback driver in the Linux kernel did not
properly handle packets structured in certain ways. An attacker in a guest
VM could possibly use this to cause a denial of service (host NIC
availability). (CVE-2022-3643)

It was discovered that an integer overflow vulnerability existed in the
Bluetooth subsystem in the Linux kernel. A physically proximate attacker
could use this to cause a denial of service (system crash).
(CVE-2022-45934)

Update instructions:

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

Ubuntu 20.04 LTS:
linux-image-5.4.0-1101-azure 5.4.0-1101.107
linux-image-azure-lts-20.04 5.4.0.1101.94

Ubuntu 18.04 LTS:
linux-image-4.15.0-1126-raspi2 4.15.0-1126.134
linux-image-5.4.0-1101-azure 5.4.0-1101.107~18.04.1
linux-image-azure 5.4.0.1101.74
linux-image-raspi2 4.15.0.1126.121

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-5830-1
CVE-2022-3643, CVE-2022-42896, CVE-2022-43945, CVE-2022-45934

Package Information:
https://launchpad.net/ubuntu/+source/linux-azure/5.4.0-1101.107
https://launchpad.net/ubuntu/+source/linux-azure-5.4/5.4.0-1101.107~18.04.1
https://launchpad.net/ubuntu/+source/linux-raspi2/4.15.0-1126.134