---
id: CVE-2026-31423
title: 'net/sched: sch_hfsc: fix divide-by-zero in rtsc_min()'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net/sched: sch_hfsc: fix divide-by-zero in rtsc_min()

  m2sm() converts a u32 slope to a u64 scaled value.  For large inputs
  (e.g. m1=4000000000), the result can reach 2…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    ad8e8fec40290a8c8cf145c0deaadf76f80c5163
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    ab1ff5890c7354afc7be56502fcfbd61f3b7ae4f
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    25b6821884713a31e2b49fb67b0ebd765b33e0a9
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    c56f78614e7781aaceca9bd3cb2128bf7d45c3bd
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    b9e6431cbea8bb1fae8069ed099b4ee100499835
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    17c1b9807b8a67d676b6dcf749ee932ebaa7f568
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    d0aefec1b1a1ba2c1d251028dc2c4e5b4ce1fea5
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    4576100b8cd03118267513cafacde164b498b322
  - Linux 2.6.12
published: '2026-04-13'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T08:47:00.059Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-31423'
references:
  - url: 'https://git.kernel.org/stable/c/ad8e8fec40290a8c8cf145c0deaadf76f80c5163'
  - url: 'https://git.kernel.org/stable/c/ab1ff5890c7354afc7be56502fcfbd61f3b7ae4f'
  - url: 'https://git.kernel.org/stable/c/25b6821884713a31e2b49fb67b0ebd765b33e0a9'
  - url: 'https://git.kernel.org/stable/c/c56f78614e7781aaceca9bd3cb2128bf7d45c3bd'
  - url: 'https://git.kernel.org/stable/c/b9e6431cbea8bb1fae8069ed099b4ee100499835'
  - url: 'https://git.kernel.org/stable/c/17c1b9807b8a67d676b6dcf749ee932ebaa7f568'
  - url: 'https://git.kernel.org/stable/c/d0aefec1b1a1ba2c1d251028dc2c4e5b4ce1fea5'
  - url: 'https://git.kernel.org/stable/c/4576100b8cd03118267513cafacde164b498b322'
tags:
  - cve.org
epss: 0.00171
epssPercentile: 0.05624
ingestedAt: '2026-09-08T15:33:26.991Z'
---

## Overview

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

net/sched: sch_hfsc: fix divide-by-zero in rtsc_min()

m2sm() converts a u32 slope to a u64 scaled value.  For large inputs
(e.g. m1=4000000000), the result can reach 2^32.  rtsc_min() stores
the difference of two such u64 values in a u32 variable `dsm` and
uses it as a divisor.  When the difference is exactly 2^32 the
truncation yields zero, causing a divide-by-zero oops in the
concave-curve intersection path:

  Oops: divide error: 0000
  RIP: 0010:rtsc_min (net/sched/sch_hfsc.c:601)
  Call Trace:
   init_ed (net/sched/sch_hfsc.c:629)
   hfsc_enqueue (net/sched/sch_hfsc.c:1569)
   [...]

Widen `dsm` to u64 and replace do_div() with div64_u64() so the full
difference is preserved.

## Affected

- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < ad8e8fec40290a8c8cf145c0deaadf76f80c5163`
- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < ab1ff5890c7354afc7be56502fcfbd61f3b7ae4f`
- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 25b6821884713a31e2b49fb67b0ebd765b33e0a9`
- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < c56f78614e7781aaceca9bd3cb2128bf7d45c3bd`
- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < b9e6431cbea8bb1fae8069ed099b4ee100499835`
- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 17c1b9807b8a67d676b6dcf749ee932ebaa7f568`
- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < d0aefec1b1a1ba2c1d251028dc2c4e5b4ce1fea5`
- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 4576100b8cd03118267513cafacde164b498b322`
- `Linux 2.6.12`

## Remediation

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