---
cve: "CVE-2023-4921"
severity: "HIGH"
cvss: 7.8
epss: "40%"
vendor: "Linux"
kev: false
exploited: false
published: "2023-09-12 20:15:10"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-09-10T22:34:41+02:00"
---

# CVE-2023-4921

> 7.8 HIGH

## Beschreibung

A use-after-free vulnerability in the Linux kernel's net/sched: sch_qfq component can be exploited to achieve local privilege escalation.

When the plug qdisc is used as a class of the qfq qdisc, sending network packets triggers use-after-free in qfq_dequeue() due to the incorrect .peek handler of sch_plug and lack of error checking in agg_dequeue().

We recommend upgrading past commit 8fc134fee27f2263988ae38920bc03da416b03d8.

## CVSS-Vektor

```
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Lokal | good |
| AC Komplexität | Gering | bad |
| PR Privilegien | Gering | warn |
| UI Interaktion | Keine | bad |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Hoch | bad |
| I Integrität | Hoch | bad |
| A Verfügbarkeit | Hoch | bad |

## Patch verfügbar (OSV)

- ffc253263a1375a65fa6c9f62a893e9767fbebfa (Commit)

## Referenzen

- <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=8fc134fee27f2263988ae38920bc03da416b03d8>
- <https://kernel.dance/8fc134fee27f2263988ae38920bc03da416b03d8>
- <https://lists.debian.org/debian-lts-announce/2023/10/msg00027.html>
- <https://lists.debian.org/debian-lts-announce/2024/01/msg00004.html>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2023-4921) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_