[USN-7860-4] Linux kernel (Real-time) vulnerability

[Rodrigo Figueiredo Zaiden]

==========================================================================
Ubuntu Security Notice USN-7860-4
November 07, 2025

linux-intel-iot-realtime, linux-realtime vulnerability
==========================================================================

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

- Ubuntu 22.04 LTS

Summary:

The system could be made to expose sensitive information.

Software Description:
- linux-intel-iot-realtime: Linux kernel for Intel IoT Real-time platforms
- linux-realtime: 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 22.04 LTS
   linux-image-5.15.0-1088-intel-iot-realtime  5.15.0-1088.90
                                   Available with Ubuntu Pro
   linux-image-5.15.0-1095-realtime  5.15.0-1095.104
                                   Available with Ubuntu Pro
   linux-image-intel-iot-realtime  5.15.0.1088.92
                                   Available with Ubuntu Pro
   linux-image-intel-iot-realtime-5.15  5.15.0.1088.92
                                   Available with Ubuntu Pro
   linux-image-realtime            5.15.0.1095.99
                                   Available with Ubuntu Pro
   linux-image-realtime-5.15       5.15.0.1095.99
                                   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-7860-4
   https://ubuntu.com/security/notices/USN-7860-3
   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-intel-iot-realtime/5.15.0-1088.90
   https://launchpad.net/ubuntu/+source/linux-realtime/5.15.0-1095.104

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