---
id: CVE-2023-4623
title: >-
  A use-after-free vulnerability in the Linux kernel's net/sched: sch_hfsc (HFSC
  qdisc traffic control) component can be exploited to achieve local privilege
  escalation.


  If a class with a link-sharing curve (i.e
summary: >-
  A use-after-free vulnerability in the Linux kernel's net/sched: sch_hfsc (HFSC
  qdisc traffic control) component can be exploited to achieve local privilege
  escalation.


  If a class with a link-sharing curve (i.e. with the HFSC_FSC flag se…
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-416
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 2.6.12, < 4.14.327'
  - 'linux_kernel >= 4.15, < 4.19.295'
  - 'linux_kernel >= 4.20, < 5.4.257'
  - 'linux_kernel >= 5.5, < 5.10.195'
  - 'linux_kernel >= 5.11, < 5.15.132'
  - 'linux_kernel >= 5.16, < 6.1.53'
  - 'linux_kernel >= 6.2, < 6.4.16'
  - 'linux_kernel >= 6.5, < 6.5.3'
  - debian_linux = 10.0
patched:
  - linux_kernel 6.5.3
published: '2023-09-06'
updated: '2026-10-14'
sourceUpdated: '2026-10-14T22:17:17.570'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2023-4623'
references:
  - url: >-
      http://packetstormsecurity.com/files/175963/Kernel-Live-Patch-Security-Notice-LSN-0099-1.html
    label: cve-coordination@google.com
  - url: >-
      https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b3d26c5702c7d6c45456326e56d2ccf3f103e60f
    label: cve-coordination@google.com
  - url: 'https://kernel.dance/b3d26c5702c7d6c45456326e56d2ccf3f103e60f'
    label: cve-coordination@google.com
  - url: 'https://lists.debian.org/debian-lts-announce/2023/10/msg00027.html'
    label: cve-coordination@google.com
  - url: 'https://lists.debian.org/debian-lts-announce/2024/01/msg00004.html'
    label: cve-coordination@google.com
  - url: >-
      http://packetstormsecurity.com/files/175963/Kernel-Live-Patch-Security-Notice-LSN-0099-1.html
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b3d26c5702c7d6c45456326e56d2ccf3f103e60f
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://kernel.dance/b3d26c5702c7d6c45456326e56d2ccf3f103e60f'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://lists.debian.org/debian-lts-announce/2023/10/msg00027.html'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://lists.debian.org/debian-lts-announce/2024/01/msg00004.html'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-398330.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-769027.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-794697.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
tags:
  - nvd
  - cve.org
epss: 0.00282
epssPercentile: 0.19282
ingestedAt: '2026-10-14T23:00:02.002Z'
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2025-02-26T21:52:35.435762Z'
---

## Overview

A use-after-free vulnerability in the Linux kernel's net/sched: sch_hfsc (HFSC qdisc traffic control) component can be exploited to achieve local privilege escalation.

If a class with a link-sharing curve (i.e. with the HFSC_FSC flag set) has a parent without a link-sharing curve, then init_vf() will call vttree_insert() on the parent, but vttree_remove() will be skipped in update_vf(). This leaves a dangling pointer that can cause a use-after-free.

We recommend upgrading past commit b3d26c5702c7d6c45456326e56d2ccf3f103e60f.

## Affected

- `linux_kernel >= 2.6.12, < 4.14.327`
- `linux_kernel >= 4.15, < 4.19.295`
- `linux_kernel >= 4.20, < 5.4.257`
- `linux_kernel >= 5.5, < 5.10.195`
- `linux_kernel >= 5.11, < 5.15.132`
- `linux_kernel >= 5.16, < 6.1.53`
- `linux_kernel >= 6.2, < 6.4.16`
- `linux_kernel >= 6.5, < 6.5.3`
- `debian_linux = 10.0`

## Remediation

Upgrade past the affected range:

- `linux_kernel 6.5.3`