---
id: CVE-2026-89920
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  KVM: s390: Fix memory corruption by not reinjecting CK machine checks

  Channel-subsystem damage machine checks are for the host channel
  subsystem
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  KVM: s390: Fix memory corruption by not reinjecting CK machine checks

  Channel-subsystem damage machine checks are for the host channel
  subsystem. The guest channel sub…
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H'
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 4d62fcc0b692e3b4058d7d138114c27cd8b011f7 <
    6ee52d3af2a1bf70349cf3f860933c8d221e229a
  - >-
    Linux >= 4d62fcc0b692e3b4058d7d138114c27cd8b011f7 <
    7077ec953996acc04b49d1dfc43df1c1a2a74395
  - >-
    Linux >= 4d62fcc0b692e3b4058d7d138114c27cd8b011f7 <
    546dde823a36d7283dcf46127c2f3d093443860f
  - Linux 4.13
published: '2026-09-16'
updated: '2026-09-16'
sourceUpdated: '2026-09-16T15:18:18.237'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89920'
references:
  - url: 'https://git.kernel.org/stable/c/546dde823a36d7283dcf46127c2f3d093443860f'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/6ee52d3af2a1bf70349cf3f860933c8d221e229a'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/7077ec953996acc04b49d1dfc43df1c1a2a74395'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-16T10:53:53.972Z'
epss: 0.00161
epssPercentile: 0.05763
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

KVM: s390: Fix memory corruption by not reinjecting CK machine checks

Channel-subsystem damage machine checks are for the host channel
subsystem. The guest channel subsystem is emulated in the userspace VMM.
There is no point in forwarding such machine checks into the guest.

This also simplifies the machine check reinjection and avoids kfree of a
stack variable as reported by sashiko.  There might be still machine
checks that have the ck bit set with another bit (like instruction
damage), mask out the CK bit in s390_backup_mcck_info(), like the CP and
ED bits already are.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.