---
id: CVE-2025-37913
title: >-
  kernel: net_sched: qfq: Fix double list add in class with netem as child qdisc
  (CVE-2025-37913)
summary: >-
  A flaw was found in the Linux kernel's Quick Fair Queueing (QFQ) network
  traffic scheduler. When nested queuing disciplines trigger reentrant packet
  enqueue operations, the scheduler fails to verify whether a class is already
  active before…
severity: medium
cvss: 6.3
cvssVector: 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:H'
cvssSource: vendor
cwe: CWE-367
vendor: Red Hat
product: Red Hat Enterprise Linux 8
affected:
  - enterprise_linux 6
  - enterprise_linux 7
  - enterprise_linux 8
published: '2025-05-20'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T22:55:33+00:00'
source: CSAF
sourceUrl: 'https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-37913.json'
references:
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-37913.json
  - url: 'https://access.redhat.com/security/cve/CVE-2025-37913'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2367518'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2025-37913'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2025-37913'
  - url: >-
      https://lore.kernel.org/linux-cve-announce/2025052000-CVE-2025-37913-95be@gregkh/T
  - url: 'https://git.kernel.org/stable/c/041f410aec2c1751ee22b8b73ba05d38c3a6a602'
  - url: 'https://git.kernel.org/stable/c/005a479540478a820c52de098e5e767e63e36f0a'
  - url: 'https://git.kernel.org/stable/c/0bf32d6fb1fcbf841bb9945570e0e2a70072c00f'
  - url: 'https://git.kernel.org/stable/c/0aa23e0856b7cedb3c88d8e3d281c212c7e4fbeb'
  - url: 'https://git.kernel.org/stable/c/a43783119e01849fbf2fe8855634e8989b240cb4'
  - url: 'https://git.kernel.org/stable/c/53bc0b55178bd59bdd4bcd16349505cabf54b1a2'
  - url: 'https://git.kernel.org/stable/c/370218e8ce711684acc4cdd3cc3c6dd7956bc165'
  - url: 'https://git.kernel.org/stable/c/f139f37dcdf34b67f5bf92bc8e0f7f6b3ac63aa4'
tags:
  - csaf
  - vex
  - red-hat
  - cve.org
epss: 0.00237
epssPercentile: 0.13748
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-10-15T21:45:52.578125Z'
scores:
  vendor: 6.3
  cna: 7.8
ingestedAt: '2026-10-15T22:48:25.482Z'
---

## Overview

A flaw was found in the Linux kernel's Quick Fair Queueing (QFQ) network traffic scheduler. When nested queuing disciplines trigger reentrant packet enqueue operations, the scheduler fails to verify whether a class is already active before adding it, resulting in duplicate list insertion. A local user could exploit this flaw to cause memory corruption, leading to a system crash and Denial of Service (DoS).

## Vendor advisories

- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8 · updated 2026-10-16 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-37913.json)

**kernel: net_sched: qfq: Fix double list add in class with netem as child qdisc** — rated Moderate by Red Hat. Released 2025-05-20, updated 2026-10-16.

Affected:

- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7
- Red Hat Enterprise Linux 8

No fix planned:

- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7
- Red Hat Enterprise Linux 8

Not affected:

- Red Hat Enterprise Linux 10
- Red Hat Enterprise Linux 9

## Remediation

Out of support scope

Workarounds / mitigations:

- Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.