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Ubuntu Security Notice USN-7854-1
October 30, 2025

linux-kvm vulnerabilities
==========================================================================

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

- Ubuntu 18.04 LTS

Summary:

Several security issues were fixed in the Linux kernel.

Software Description:
- 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 layer;
   - Packet sockets;
   - Network traffic control;
   - SCTP protocol;
   - VMware vSockets driver;
   - USB sound devices;
(CVE-2023-52574, CVE-2023-52650, CVE-2024-35849, CVE-2024-41006,
CVE-2024-49924, CVE-2024-50006, CVE-2024-50299, CVE-2024-53124,
CVE-2024-53150, CVE-2024-56767, CVE-2025-21796, CVE-2025-37785,
CVE-2025-37838, CVE-2025-38352, CVE-2025-38477, CVE-2025-38617,
CVE-2025-38618)

Update instructions:

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

Ubuntu 18.04 LTS
   linux-image-4.15.0-1168-kvm     4.15.0-1168.173
                                   Available with Ubuntu Pro
   linux-image-kvm                 4.15.0.1168.159
                                   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-7854-1
   CVE-2023-52574, CVE-2023-52650, CVE-2024-35849, CVE-2024-41006,
   CVE-2024-49924, CVE-2024-50006, CVE-2024-50299, CVE-2024-53124,
   CVE-2024-53150, CVE-2024-56767, CVE-2025-21796, CVE-2025-37785,
   CVE-2025-37838, CVE-2025-38352, CVE-2025-38477, CVE-2025-38617,
   CVE-2025-38618, CVE-2025-40300