1. Ubuntu Security Notices
  2. USN-7861-2

USN-7861-2: Linux kernel (Real-time) vulnerabilities

Publication date

7 November 2025

Overview

Several security issues were fixed in the Linux kernel.

Releases

Packages

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.

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:

  • HSI subsystem;
  • Bluetooth subsystem;
  • Timer subsystem

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.

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:

  • HSI subsystem;
  • Bluetooth subsystem;
  • Timer subsystem

Update instructions

After a standard system update you need to reboot your computer to make all the necessary changes.

Learn more about how to get the fixes.

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.

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

Ubuntu Release Package Version
24.04 LTS noble linux-image-6.8.1-1037-realtime –  6.8.1-1037.38  
linux-image-realtime –  6.8.1-1037.38  
linux-image-realtime-6.8.1 –  6.8.1-1037.38  
22.04 LTS jammy linux-image-6.8.1-1037-realtime –  6.8.1-1037.38~22.04.1  
linux-image-realtime-6.8.1 –  6.8.1-1037.38~22.04.1  
linux-image-realtime-hwe-22.04 –  6.8.1-1037.38~22.04.1  

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References

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