---
id: CVE-2026-90072
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net/sched: sfq: clamp quantum to avoid signed overflow soft lockup

  sfq_init() sets q->quantum = psched_mtu(qdisc_dev(sch)) (unsigned)
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net/sched: sfq: clamp quantum to avoid signed overflow soft lockup

  sfq_init() sets q->quantum = psched_mtu(qdisc_dev(sch)) (unsigned). A
  device with a huge MTU (e.g. d…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    86799499585af06a9431c9e7782658667bd62650
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    2017c355a5a1af77736cd1739fe922f69b5652dc
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    6581a82bf08ba5d4e2a6d4e3080df43315b296c4
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    9d782c662879c3adaaca30e05c36910ad11b9e54
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    d72dbdfaeb5b9b8d884e0e036c3442754379ef74
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    aeb8196ecb95146e3410f635628e6cd47352b3e5
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    da16c31517cd2c06bb2c78c73e91ae192c01c426
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    816e90057ab1879562a5b7cc688e35bb9027ae97
  - Linux 2.6.12
published: '2026-09-17'
updated: '2026-09-17'
sourceUpdated: '2026-09-17T17:16:56.250'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-90072'
references:
  - url: 'https://git.kernel.org/stable/c/2017c355a5a1af77736cd1739fe922f69b5652dc'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/6581a82bf08ba5d4e2a6d4e3080df43315b296c4'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/816e90057ab1879562a5b7cc688e35bb9027ae97'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/86799499585af06a9431c9e7782658667bd62650'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/9d782c662879c3adaaca30e05c36910ad11b9e54'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/aeb8196ecb95146e3410f635628e6cd47352b3e5'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/d72dbdfaeb5b9b8d884e0e036c3442754379ef74'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/da16c31517cd2c06bb2c78c73e91ae192c01c426'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-17T16:21:47.897Z'
epss: 0.0022
epssPercentile: 0.11037
---

## Overview

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

net/sched: sfq: clamp quantum to avoid signed overflow soft lockup

sfq_init() sets q->quantum = psched_mtu(qdisc_dev(sch)) (unsigned). A
device with a huge MTU (e.g. dummy with max_mtu == 0 accepting MTU
2147483634) makes psched_mtu() return 0x80000000, so slot->allot = INT_MIN
and INT_MIN + INT_MIN toggles between INT_MIN and 0 forever, spinning
sfq_dequeue() under the qdisc lock.

Clamp the quantum to [256, 1 << 20] so the refill loop terminates. The
lower bound also covers q->quantum == 0 (psched_mtu() returning 0),
which spins sfq_dequeue() identically. sfq_change() already rejects a
negative quantum, so only the init path was exposed.

Conditions to recreate the bug: a device whose MTU (plus
hard_header_len) wraps psched_mtu() into the sign bit (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.