1. Ubuntu Security Notices
  2. USN-7854-1

USN-7854-1: Linux kernel (KVM) vulnerabilities

Publication date

30 October 2025

Overview

Several security issues were fixed in the Linux kernel.

Releases

Packages

  • linux-kvm - Linux kernel for cloud environments

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. (CVE-2025-40300)

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:

  • DMA engine subsystem;
  • GPU drivers;
  • HSI subsystem;
  • Ethernet team driver;
  • Framebuffer layer;
  • BTRFS file system;
  • Ext4 file system;
  • Network file system (NFS) server daemon;
  • Timer subsystem;
  • DCCP (Datagram Congestion Control Protocol);
  • IPv6 networking;
  • NET/ROM...

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. (CVE-2025-40300)

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:

  • DMA engine subsystem;
  • GPU drivers;
  • HSI subsystem;
  • Ethernet team driver;
  • Framebuffer layer;
  • BTRFS file system;
  • Ext4 file system;
  • Network file system (NFS) server daemon;
  • Timer subsystem;
  • DCCP (Datagram Congestion Control Protocol);
  • IPv6 networking;
  • NET/ROM layer;
  • Packet sockets;
  • Network traffic control;
  • SCTP protocol;
  • VMware vSockets driver;
  • USB sound devices

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
18.04 LTS bionic linux-image-4.15.0-1168-kvm –  4.15.0-1168.173  
linux-image-kvm –  4.15.0.1168.159  

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References

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