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Ubuntu 20.04 LTS Linux Kernel USN-8255-2 Critical Local Escalation

ubuntu
Calendar Grey May 11, 2026
Dist Ubuntu Esm H88
Several critical security fixes for the Ubuntu 20.04 LTS kernel address local privilege escalation risks.
Several security issues were fixed in the Linux kernel.

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)

Topics%20covered

Topics Covered

security advisory critical local privilege escalation Ubuntu kernel overlayfs

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

Severity
critical
Lowest
Low
Medium
High
Critical

Ubuntu Security Notice USN-8255-2

Topics%20covered

Topics Covered

security advisory critical local privilege escalation Ubuntu kernel overlayfs

Package Information

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