---
id: CVE-2026-89965
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  nvdimm/btt: reject an arena whose nfree is below the lane count

  The BTT info block's nfree field, the number of reserve free blocks, is
  read from the medium without va…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  nvdimm/btt: reject an arena whose nfree is below the lane count

  The BTT info block's nfree field, the number of reserve free blocks, is
  read from the medium without va…
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 5212e11fde4d40fa627668b4f2222d20db488f71 <
    eb491343d2d1784121ad9af91c25b338c28913c3
  - >-
    Linux >= 5212e11fde4d40fa627668b4f2222d20db488f71 <
    59d5cd1f42b4bab3609512c3cb3d3540d3d21da7
  - >-
    Linux >= 5212e11fde4d40fa627668b4f2222d20db488f71 <
    f6c5313aae794ecca8f762c1a3493de5c266f120
  - >-
    Linux >= 5212e11fde4d40fa627668b4f2222d20db488f71 <
    f9bf05c63b77d000e9c01f3e47af36973887d350
  - >-
    Linux >= 5212e11fde4d40fa627668b4f2222d20db488f71 <
    6f79d1a5f2611a3d36e9312be5425cd9cb397c51
  - >-
    Linux >= 5212e11fde4d40fa627668b4f2222d20db488f71 <
    6b1faf1f099f7060b5f1f2f0d024132581f1726e
  - >-
    Linux >= 5212e11fde4d40fa627668b4f2222d20db488f71 <
    9dfa11cef4750b67591307f2c62e47a23d60e4b7
  - >-
    Linux >= 5212e11fde4d40fa627668b4f2222d20db488f71 <
    6a1f2e5ed9267ca19187038ac635393c165213ac
  - Linux 4.2
published: '2026-09-16'
updated: '2026-09-16'
sourceUpdated: '2026-09-16T15:18:20.830'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89965'
references:
  - url: 'https://git.kernel.org/stable/c/59d5cd1f42b4bab3609512c3cb3d3540d3d21da7'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/6a1f2e5ed9267ca19187038ac635393c165213ac'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/6b1faf1f099f7060b5f1f2f0d024132581f1726e'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/6f79d1a5f2611a3d36e9312be5425cd9cb397c51'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/9dfa11cef4750b67591307f2c62e47a23d60e4b7'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/eb491343d2d1784121ad9af91c25b338c28913c3'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/f6c5313aae794ecca8f762c1a3493de5c266f120'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/f9bf05c63b77d000e9c01f3e47af36973887d350'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-16T10:53:53.958Z'
epss: 0.00164
epssPercentile: 0.06052
---

## Overview

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

nvdimm/btt: reject an arena whose nfree is below the lane count

The BTT info block's nfree field, the number of reserve free blocks, is
read from the medium without validation.  btt_freelist_init() and
btt_rtt_init() size the per-lane freelist[] and rtt[] arrays by nfree,
but the I/O path indexes them by the lane from nd_region_acquire_lane(),
which is bounded by nd_region->num_lanes (ND_MAX_LANES), not by nfree.
A crafted or foreign arena whose nfree is below the lane count makes
freelist[lane]/rtt[lane] run past the allocation: an out-of-bounds write.

btt.rst documents the nlanes = min(nfree, num_cpus) invariant, which the
code does not currently honor: num_lanes is ND_MAX_LANES regardless of
nfree.  Reject an arena whose nfree is below num_lanes at discovery,
before the per-lane arrays are allocated, enforcing that invariant.

## Remediation

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