---
id: CVE-2025-40348
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  slab: Avoid race on slab->obj_exts in alloc_slab_obj_exts

  If two competing threads enter alloc_slab_obj_exts() and one of them
  fails to allocate the object extension v…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  slab: Avoid race on slab->obj_exts in alloc_slab_obj_exts

  If two competing threads enter alloc_slab_obj_exts() and one of them
  fails to allocate the object extension v…
severity: none
published: '2025-12-16'
updated: '2026-10-14'
sourceUpdated: '2026-10-14T13:10:00.187'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-40348'
references:
  - url: 'https://git.kernel.org/stable/c/6ed8bfd24ce1cb31742b09a3eb557cd008533eec'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/7c34feda6a9a203c9744281f1b6671b7dad2012d'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/c7af5300d78460fc5037ddc77113ba3dbfe77dc0'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
epss: 0.00199
epssPercentile: 0.08999
ingestedAt: '2026-10-14T13:30:58.437Z'
---

## Overview

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

slab: Avoid race on slab->obj_exts in alloc_slab_obj_exts

If two competing threads enter alloc_slab_obj_exts() and one of them
fails to allocate the object extension vector, it might override the
valid slab->obj_exts allocated by the other thread with
OBJEXTS_ALLOC_FAIL. This will cause the thread that lost this race and
expects a valid pointer to dereference a NULL pointer later on.

Update slab->obj_exts atomically using cmpxchg() to avoid
slab->obj_exts overrides by racing threads.

Thanks for Vlastimil and Suren's help with debugging.

## Remediation

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