---
id: CVE-2023-31436
title: >-
  qfq_change_class in net/sched/sch_qfq.c in the Linux kernel before 6.2.13
  allows an out-of-bounds write because lmax can exceed QFQ_MIN_LMAX.
summary: >-
  qfq_change_class in net/sched/sch_qfq.c in the Linux kernel before 6.2.13
  allows an out-of-bounds write because lmax can exceed QFQ_MIN_LMAX.
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'
cwe:
  - CWE-787
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 3.7, < 4.14.314'
  - 'linux_kernel >= 4.15, < 4.19.282'
  - 'linux_kernel >= 4.20, < 5.4.242'
  - 'linux_kernel >= 5.5.0, < 5.10.179'
  - 'linux_kernel >= 5.11, < 5.15.109'
  - 'linux_kernel >= 5.16, < 6.1.26'
  - 'linux_kernel >= 6.2, < 6.2.13'
patched:
  - linux_kernel 6.2.13
published: '2023-04-28'
updated: '2026-10-14'
sourceUpdated: '2026-10-14T23:17:18.727'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2023-31436'
references:
  - url: >-
      http://packetstormsecurity.com/files/173087/Kernel-Live-Patch-Security-Notice-LSN-0095-1.html
    label: cve@mitre.org
  - url: >-
      http://packetstormsecurity.com/files/173757/Kernel-Live-Patch-Security-Notice-LSN-0096-1.html
    label: cve@mitre.org
  - url: >-
      http://packetstormsecurity.com/files/175963/Kernel-Live-Patch-Security-Notice-LSN-0099-1.html
    label: cve@mitre.org
  - url: 'https://cdn.kernel.org/pub/linux/kernel/v6.x/ChangeLog-6.2.13'
    label: cve@mitre.org
  - url: >-
      https://github.com/torvalds/linux/commit/3037933448f60f9acb705997eae62013ecb81e0d
    label: cve@mitre.org
  - url: 'https://lists.debian.org/debian-lts-announce/2023/06/msg00008.html'
    label: cve@mitre.org
  - url: 'https://security.netapp.com/advisory/ntap-20230609-0001/'
    label: cve@mitre.org
  - url: 'https://www.debian.org/security/2023/dsa-5402'
    label: cve@mitre.org
  - url: 'https://www.spinics.net/lists/stable-commits/msg294885.html'
    label: cve@mitre.org
  - url: >-
      http://packetstormsecurity.com/files/173087/Kernel-Live-Patch-Security-Notice-LSN-0095-1.html
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      http://packetstormsecurity.com/files/173757/Kernel-Live-Patch-Security-Notice-LSN-0096-1.html
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      http://packetstormsecurity.com/files/175963/Kernel-Live-Patch-Security-Notice-LSN-0099-1.html
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://cdn.kernel.org/pub/linux/kernel/v6.x/ChangeLog-6.2.13'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://github.com/torvalds/linux/commit/3037933448f60f9acb705997eae62013ecb81e0d
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://lists.debian.org/debian-lts-announce/2023/06/msg00008.html'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://security.netapp.com/advisory/ntap-20230609-0001/'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://www.debian.org/security/2023/dsa-5402'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://www.spinics.net/lists/stable-commits/msg294885.html'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-794697.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-806742.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
tags:
  - nvd
  - cve.org
epss: 0.00598
epssPercentile: 0.48414
ingestedAt: '2026-10-15T00:02:07.133Z'
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2024-10-15T17:15:52.761316Z'
---

## Overview

qfq_change_class in net/sched/sch_qfq.c in the Linux kernel before 6.2.13 allows an out-of-bounds write because lmax can exceed QFQ_MIN_LMAX.

## Affected

- `linux_kernel >= 3.7, < 4.14.314`
- `linux_kernel >= 4.15, < 4.19.282`
- `linux_kernel >= 4.20, < 5.4.242`
- `linux_kernel >= 5.5.0, < 5.10.179`
- `linux_kernel >= 5.11, < 5.15.109`
- `linux_kernel >= 5.16, < 6.1.26`
- `linux_kernel >= 6.2, < 6.2.13`

## Remediation

Upgrade past the affected range:

- `linux_kernel 6.2.13`