---
id: CVE-2021-33656
title: >-
  When setting font with malicous data by ioctl cmd PIO_FONT,kernel will write
  memory out of bounds.
summary: >-
  When setting font with malicous data by ioctl cmd PIO_FONT,kernel will write
  memory out of bounds.
severity: medium
cvss: 6.8
cvssVector: 'CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'
cwe:
  - CWE-787
  - CWE-787
vendor: openatom
product: openeuler
affected:
  - openeuler = 20.03
  - linux_kernel < 5.10.127
  - debian_linux = 10.0
patched:
  - linux_kernel 5.10.127
published: '2022-07-18'
updated: '2026-10-08'
sourceUpdated: '2026-10-08T22:17:10.127'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2021-33656'
references:
  - url: 'http://www.openwall.com/lists/oss-security/2022/07/19/3'
    label: securities@openeuler.org
  - url: >-
      https://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git/tree/releases/5.10.127/vt-drop-old-font-ioctls.patch
    label: securities@openeuler.org
  - url: 'https://lists.debian.org/debian-lts-announce/2022/10/msg00000.html'
    label: securities@openeuler.org
  - url: >-
      https://www.openeuler.org/en/security/cve/detail.html?id=CVE-2021-33656&packageName=kernel
    label: securities@openeuler.org
  - url: 'http://www.openwall.com/lists/oss-security/2022/07/19/3'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git/tree/releases/5.10.127/vt-drop-old-font-ioctls.patch
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://lists.debian.org/debian-lts-announce/2022/10/msg00000.html'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://www.openeuler.org/en/security/cve/detail.html?id=CVE-2021-33656&packageName=kernel
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.00611
epssPercentile: 0.47668
ingestedAt: '2026-10-08T23:16:47.346Z'
---

## Overview

When setting font with malicous data by ioctl cmd PIO_FONT,kernel will write memory out of bounds.

## Affected

- `openeuler = 20.03`
- `linux_kernel < 5.10.127`
- `debian_linux = 10.0`

## Remediation

Upgrade past the affected range:

- `linux_kernel 5.10.127`