---
id: CVE-2026-90076
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net/sched: fq: add overflow bounds to quantum and initial quantum

  fq_init() computes quantum = 2 * psched_mtu() and initial_quantum = 10 *
  psched_mtu() with no overflo…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net/sched: fq: add overflow bounds to quantum and initial quantum

  fq_init() computes quantum = 2 * psched_mtu() and initial_quantum = 10 *
  psched_mtu() with no overflo…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= afe4fd062416b158a8a8538b23adc1930a9b88dc <
    d16dac3925be95ad46e986d4b139c9898b6e227f
  - >-
    Linux >= afe4fd062416b158a8a8538b23adc1930a9b88dc <
    f6b3e3848a5fca63438984acd6d9eceac80814c1
  - >-
    Linux >= afe4fd062416b158a8a8538b23adc1930a9b88dc <
    e35acd56f244d94355f9ab237c2ecc8fba5e6f04
  - >-
    Linux >= afe4fd062416b158a8a8538b23adc1930a9b88dc <
    709f34f7c28dc4dd6c40343d101850f11e172312
  - Linux 3.12
published: '2026-09-17'
updated: '2026-09-17'
sourceUpdated: '2026-09-17T17:16:56.820'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-90076'
references:
  - url: 'https://git.kernel.org/stable/c/709f34f7c28dc4dd6c40343d101850f11e172312'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/d16dac3925be95ad46e986d4b139c9898b6e227f'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/e35acd56f244d94355f9ab237c2ecc8fba5e6f04'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/f6b3e3848a5fca63438984acd6d9eceac80814c1'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-17T16:21:47.897Z'
epss: 0.00209
epssPercentile: 0.09794
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

net/sched: fq: add overflow bounds to quantum and initial quantum

fq_init() computes quantum = 2 * psched_mtu() and initial_quantum = 10 *
psched_mtu() with no overflow check. A device with a huge MTU (e.g. dummy
with max_mtu == 0 accepting MTU 2147483634) makes psched_mtu() return
0x80000000; the 2 * and 10 * multiplications wrap to 0 in 32-bit
arithmetic, so q->quantum == 0. Then in fq_dequeue() the credit-refill
loop adds 0 to f->credit (which stays <= 0) and goto begin loops
forever under the qdisc lock, creating a soft lockup.

Clamp psched_mtu() to [1, 1 << 20] before multiplying so the product
cannot wrap, then cap the result at 1 << 20, matching the bound already
enforced on TCA_FQ_QUANTUM in fq_change().

Conditions to recreate the bug: a device whose MTU (plus
hard_header_len) is large enough that 2 * psched_mtu() wraps (e.g. a
dummy device with max_mtu == 0 accepting MTU 2147483634). Requires
CAP_NET_ADMIN in a user namespace.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.