[USN-8201-1] Linux kernel (Azure) vulnerabilities

[Rodrigo Figueiredo Zaiden]

==========================================================================
Ubuntu Security Notice USN-8201-1
April 22, 2026

linux-azure-5.4 vulnerabilities
==========================================================================

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

- Ubuntu 18.04 LTS

Summary:

Several security issues were fixed in the Linux kernel.

Software Description:
- linux-azure-5.4: Linux kernel for Microsoft Azure cloud systems

Details:

Qualys discovered that several vulnerabilities existed in the AppArmor
Linux kernel Security Module (LSM). An unprivileged local attacker could
use these issues to load, replace, and remove arbitrary AppArmor profiles
causing denial of service, exposure of sensitive information (kernel
memory), local privilege escalation, or possibly escape a container.
(LP: #2143853, CVE-2026-23268, CVE-2026-23269, CVE-2026-23403,
CVE-2026-23404, CVE-2026-23405, CVE-2026-23406, CVE-2026-23407,
CVE-2026-23408, CVE-2026-23409, CVE-2026-23410, CVE-2026-23411)

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:
   - ARM64 architecture;
   - x86 architecture;
   - Cryptographic API;
   - GPIO subsystem;
   - GPU drivers;
   - I2C subsystem;
   - BTRFS file system;
   - XFRM subsystem;
   - IPv4 networking;
   - IPv6 networking;
   - MAC80211 subsystem;
   - Network traffic control;
   - SMC sockets;
(CVE-2021-47599, CVE-2022-48875, CVE-2022-49046, CVE-2022-49072,
CVE-2024-46816, CVE-2024-49927, CVE-2024-56640, CVE-2025-21780,
CVE-2025-37849, CVE-2025-40215, CVE-2026-23060, CVE-2026-23074)

Update instructions:

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

Ubuntu 18.04 LTS
   linux-image-5.4.0-1161-azure    5.4.0-1161.167~18.04.1
                                   Available with Ubuntu Pro
   linux-image-azure               5.4.0.1161.167~18.04.1
                                   Available with Ubuntu Pro
   linux-image-azure-5.4           5.4.0.1161.167~18.04.1
                                   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-8201-1
   https://launchpad.net/bugs/2143853
   CVE-2021-47599, CVE-2022-48875, CVE-2022-49046, CVE-2022-49072,
   CVE-2024-46816, CVE-2024-49927, CVE-2024-56640, CVE-2025-21780,
   CVE-2025-37849, CVE-2025-40215, CVE-2026-23060, CVE-2026-23074,
   CVE-2026-23268, CVE-2026-23269, CVE-2026-23403, CVE-2026-23404,
   CVE-2026-23405, CVE-2026-23406, CVE-2026-23407, CVE-2026-23409,
   CVE-2026-23410, CVE-2026-23411

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