[USN-7860-2] Linux kernel (Real-time) vulnerability

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==========================================================================
Ubuntu Security Notice USN-7860-2
November 06, 2025

linux-realtime-6.14 vulnerability
==========================================================================

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

- Ubuntu 24.04 LTS

Summary:

The system could be made to expose sensitive information.

Software Description:
- linux-realtime-6.14: Linux kernel for Real-time 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.

Update instructions:

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

Ubuntu 24.04 LTS
linux-image-6.14.0-1015-realtime 6.14.0-1015.15~24.04.1
Available with Ubuntu Pro
linux-image-realtime-6.14 6.14.0-1015.15~24.04.1
Available with Ubuntu Pro
linux-image-realtime-hwe-24.04 6.14.0-1015.15~24.04.1
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-7860-2
https://ubuntu.com/security/notices/USN-7860-1
CVE-2025-40300

Package Information:

https://launchpad.net/ubuntu/+source/linux-realtime-6.14/6.14.0-1015.15~24.04.1