==========================================================================
Ubuntu Security Notice USN-7939-1
December 16, 2025

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

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

Details:

Jean-Claude Graf, Sandro Rüegge, Ali Hajiabadi, and Kaveh Razavi discovered
that the Linux kernel contained insufficient branch predictor isolation
between a guest and a userspace hypervisor for certain processors. This
flaw is known as VMSCAPE. An attacker in a guest VM could possibly use this
to expose sensitive information from the host OS. (CVE-2025-40300)

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:
   - Cryptographic API;
   - ACPI drivers;
   - HSI subsystem;
   - I3C subsystem;
   - InfiniBand drivers;
   - Media drivers;
   - Network drivers;
   - Pin controllers subsystem;
   - AFS file system;
   - F2FS file system;
   - SMB network file system;
   - Padata parallel execution mechanism;
   - Timer subsystem;
   - Tracing infrastructure;
   - Memory management;
   - Appletalk network protocol;
   - Networking core;
   - Netfilter;
(CVE-2022-49026, CVE-2022-49390, CVE-2023-52854, CVE-2024-35867,
CVE-2024-47691, CVE-2024-49935, CVE-2024-50061, CVE-2024-50067,
CVE-2024-50095, CVE-2024-50196, CVE-2024-53090, CVE-2024-53218,
CVE-2024-56664, CVE-2025-21727, CVE-2025-21855, CVE-2025-37838,
CVE-2025-37958, CVE-2025-38352, CVE-2025-38666, CVE-2025-39964,
CVE-2025-39993, CVE-2025-40018)

Update instructions:

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

Ubuntu 20.04 LTS
   linux-image-5.4.0-1156-azure    5.4.0-1156.163
                                   Available with Ubuntu Pro
   linux-image-azure-5.4           5.4.0.1156.150
                                   Available with Ubuntu Pro
   linux-image-azure-lts-20.04     5.4.0.1156.150
                                   Available with Ubuntu Pro

Ubuntu 18.04 LTS
   linux-image-5.4.0-1156-azure    5.4.0-1156.163~18.04.1
                                   Available with Ubuntu Pro
   linux-image-azure               5.4.0.1156.163~18.04.1
                                   Available with Ubuntu Pro
   linux-image-azure-5.4           5.4.0.1156.163~18.04.1
                                   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-7939-1
   CVE-2022-49026, CVE-2022-49390, CVE-2023-52854, CVE-2024-35867,
   CVE-2024-47691, CVE-2024-49935, CVE-2024-50061, CVE-2024-50067,
   CVE-2024-50095, CVE-2024-50196, CVE-2024-53090, CVE-2024-53218,
   CVE-2024-56664, CVE-2025-21727, CVE-2025-21855, CVE-2025-37838,
   CVE-2025-37958, CVE-2025-38352, CVE-2025-38666, CVE-2025-39964,
   CVE-2025-39993, CVE-2025-40018, CVE-2025-40300