[USN-7935-1] Linux kernel (Azure) vulnerabilities

[Rodrigo Figueiredo Zaiden]

==========================================================================
Ubuntu Security Notice USN-7935-1
December 15, 2025

linux-azure, linux-azure-6.8 vulnerabilities
==========================================================================

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

- Ubuntu 24.04 LTS
- Ubuntu 22.04 LTS

Summary:

Several security issues were fixed in the Linux kernel.

Software Description:
- linux-azure: Linux kernel for Microsoft Azure Cloud systems
- linux-azure-6.8: 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;
   - HSI subsystem;
   - Media drivers;
   - Network drivers;
   - Bluetooth subsystem;
   - Timer subsystem;
   - Memory management;
   - Appletalk network protocol;
   - Netfilter;
   - TLS protocol;
(CVE-2025-21729, CVE-2025-37838, CVE-2025-37958, CVE-2025-38118,
CVE-2025-38227, CVE-2025-38352, CVE-2025-38616, CVE-2025-38666,
CVE-2025-38678, 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 24.04 LTS
   linux-image-6.8.0-1044-azure    6.8.0-1044.50
   linux-image-azure-6.8           6.8.0-1044.50
   linux-image-azure-lts-24.04     6.8.0-1044.50

Ubuntu 22.04 LTS
   linux-image-6.8.0-1044-azure    6.8.0-1044.50~22.04.1
   linux-image-azure               6.8.0-1044.50~22.04.1
   linux-image-azure-6.8           6.8.0-1044.50~22.04.1

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-7935-1
   CVE-2025-21729, CVE-2025-37838, CVE-2025-37958, CVE-2025-38118,
   CVE-2025-38227, CVE-2025-38352, CVE-2025-38616, CVE-2025-38666,
   CVE-2025-38678, CVE-2025-39964, CVE-2025-39993, CVE-2025-40018,
   CVE-2025-40300

Package Information:
   https://launchpad.net/ubuntu/+source/linux-azure/6.8.0-1044.50
   https://launchpad.net/ubuntu/+source/linux-azure-6.8/6.8.0-1044.50~22.04.1

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