---
id: CVE-2021-46977
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  KVM: VMX: Disable preemption when probing user return MSRs

  Disable preemption when probing a user return MSR via RDSMR/WRMSR
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  KVM: VMX: Disable preemption when probing user return MSRs

  Disable preemption when probing a user return MSR via RDSMR/WRMSR.  If
  the MSR holds a different value per l…
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 5.5, < 5.10.38'
  - 'linux_kernel >= 5.11, < 5.11.22'
  - 'linux_kernel >= 5.12, < 5.12.5'
  - linux_kernel = 5.13
patched:
  - linux_kernel 5.12.5
published: '2024-02-28'
updated: '2026-08-04'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2021-46977'
references:
  - url: 'https://git.kernel.org/stable/c/31f29749ee970c251b3a7e5b914108425940d089'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/5104d7ffcf24749939bea7fdb5378d186473f890'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/5adcdeb57007ccf8ab7ac20bf787ffb6fafb1a94'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/e3ea1895df719c4ef87862501bb10d95f4177bed'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/31f29749ee970c251b3a7e5b914108425940d089'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://git.kernel.org/stable/c/5104d7ffcf24749939bea7fdb5378d186473f890'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://git.kernel.org/stable/c/5adcdeb57007ccf8ab7ac20bf787ffb6fafb1a94'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://git.kernel.org/stable/c/e3ea1895df719c4ef87862501bb10d95f4177bed'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.00241
epssPercentile: 0.13621
ingestedAt: '2026-08-04T10:39:38.792Z'
---

## Overview

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

KVM: VMX: Disable preemption when probing user return MSRs

Disable preemption when probing a user return MSR via RDSMR/WRMSR.  If
the MSR holds a different value per logical CPU, the WRMSR could corrupt
the host's value if KVM is preempted between the RDMSR and WRMSR, and
then rescheduled on a different CPU.

Opportunistically land the helper in common x86, SVM will use the helper
in a future commit.

## Affected

- `linux_kernel >= 5.5, < 5.10.38`
- `linux_kernel >= 5.11, < 5.11.22`
- `linux_kernel >= 5.12, < 5.12.5`
- `linux_kernel = 5.13`

## Remediation

Upgrade past the affected range:

- `linux_kernel 5.12.5`