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[USN-8255-2] Linux kernel (Azure) vulnerabilities

Posted on 11 May 2026
Ubuntu Security

==========================================================================Ubuntu Security Notice USN-8255-2
May 11, 2026

linux-azure-5.15 vulnerabilities
==========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 20.04 LTS

Summary:

Several security issues were fixed in the Linux kernel.

Software Description:
- linux-azure-5.15: Linux kernel for Microsoft Azure cloud systems

Details:

Stonejiajia, Shir Tamari and Sagi Tzadik discovered that the OverlayFS
implementation in the Ubuntu Linux kernel did not properly perform
permission checks in certain situations. A local attacker could possibly
use this to gain elevated privileges. (CVE-2023-2640)

Shir Tamari and Sagi Tzadik discovered that the OverlayFS implementation in
the Ubuntu Linux kernel did not properly perform permission checks in
certain situations. A local attacker could possibly use this to gain
elevated privileges. (CVE-2023-32629)

Several security issues were discovered in the Linux kernel.
An attacker could possibly use these to compromise the system.
This update corrects flaws in the following subsystems:
- Network drivers;
- NVME drivers;
(CVE-2026-23112, CVE-2026-23273)

Update instructions:

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

Ubuntu 20.04 LTS
linux-image-5.15.0-1111-azure 5.15.0-1111.120~20.04.1
Available with Ubuntu Pro
linux-image-azure 5.15.0.1111.120~20.04.1
Available with Ubuntu Pro
linux-image-azure-5.15 5.15.0.1111.120~20.04.1
Available with Ubuntu Pro
linux-image-azure-cvm 5.15.0.1111.120~20.04.1
Available with Ubuntu Pro

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-8255-2
https://ubuntu.com/security/notices/USN-8255-1
CVE-2023-2640, CVE-2023-32629, CVE-2026-23112, CVE-2026-23273


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