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

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

Publication date: 7 November 2025
Overview: Several security issues were fixed in the Linux kernel.

Packages
linux-realtime - Linux kernel for Real-time systems
linux-realtime-6.8 - 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.

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

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