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Ubuntu 22.04: Major Security Flaw in Linux Kernel USN-7860-4 CVE-2025-40300

ubuntu
Calendar Grey November 7, 2025
Dist Ubuntu Esm H88
Security advisory for Ubuntu addressing a critical issue in the Linux kernel that could expose sensitive information.
The system could be made to expose sensitive information.

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.

Topics%20covered

Topics Covered

security advisory critical Ubuntu information exposure Linux kernel Real Time

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

Severity
critical
Lowest
Low
Medium
High
Critical

Ubuntu Security Notice USN-7860-4

Topics%20covered

Topics Covered

security advisory critical Ubuntu information exposure Linux kernel Real Time

Package Information

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