---
id: CVE-2025-40201
title: >-
  kernel/sys.c: fix the racy usage of task_lock(tsk->group_leader) in
  sys_prlimit64() paths
summary: >-
  In the Linux kernel, the following vulnerability has been resolved:


  kernel/sys.c: fix the racy usage of task_lock(tsk->group_leader) in
  sys_prlimit64() paths


  The usage of task_lock(tsk->group_leader) in sys_prlimit64()->do_prlimit()

  pa…
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'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 18c91bb2d87268d23868bf13508f5bc9cf04e89a <
    1bc0d9315ef5296abb2c9fd840336255850ded18
  - >-
    Linux >= 18c91bb2d87268d23868bf13508f5bc9cf04e89a <
    132f827e7bac7373e1522e89709d70b43cae5342
  - >-
    Linux >= 18c91bb2d87268d23868bf13508f5bc9cf04e89a <
    19b45c84bd9fd42fa97ff80c6350d604cb871c75
  - >-
    Linux >= 18c91bb2d87268d23868bf13508f5bc9cf04e89a <
    6796412decd2d8de8ec708213bbc958fab72f143
  - >-
    Linux >= 18c91bb2d87268d23868bf13508f5bc9cf04e89a <
    a15f37a40145c986cdf289a4b88390f35efdecc4
  - Linux 5.18
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-10-15T21:58:02.275858Z'
published: '2025-11-12'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T22:02:40.564Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2025-40201'
references:
  - url: 'https://git.kernel.org/stable/c/1bc0d9315ef5296abb2c9fd840336255850ded18'
  - url: 'https://git.kernel.org/stable/c/132f827e7bac7373e1522e89709d70b43cae5342'
  - url: 'https://git.kernel.org/stable/c/19b45c84bd9fd42fa97ff80c6350d604cb871c75'
  - url: 'https://git.kernel.org/stable/c/6796412decd2d8de8ec708213bbc958fab72f143'
  - url: 'https://git.kernel.org/stable/c/a15f37a40145c986cdf289a4b88390f35efdecc4'
tags:
  - cve.org
epss: 0.00153
epssPercentile: 0.03958
ingestedAt: '2026-10-15T22:48:25.551Z'
---

## Overview

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

kernel/sys.c: fix the racy usage of task_lock(tsk->group_leader) in sys_prlimit64() paths

The usage of task_lock(tsk->group_leader) in sys_prlimit64()->do_prlimit()
path is very broken.

sys_prlimit64() does get_task_struct(tsk) but this only protects task_struct
itself. If tsk != current and tsk is not a leader, this process can exit/exec
and task_lock(tsk->group_leader) may use the already freed task_struct.

Another problem is that sys_prlimit64() can race with mt-exec which changes
->group_leader. In this case do_prlimit() may take the wrong lock, or (worse)
->group_leader may change between task_lock() and task_unlock().

Change sys_prlimit64() to take tasklist_lock when necessary. This is not
nice, but I don't see a better fix for -stable.

## Affected

- `Linux >= 18c91bb2d87268d23868bf13508f5bc9cf04e89a < 1bc0d9315ef5296abb2c9fd840336255850ded18`
- `Linux >= 18c91bb2d87268d23868bf13508f5bc9cf04e89a < 132f827e7bac7373e1522e89709d70b43cae5342`
- `Linux >= 18c91bb2d87268d23868bf13508f5bc9cf04e89a < 19b45c84bd9fd42fa97ff80c6350d604cb871c75`
- `Linux >= 18c91bb2d87268d23868bf13508f5bc9cf04e89a < 6796412decd2d8de8ec708213bbc958fab72f143`
- `Linux >= 18c91bb2d87268d23868bf13508f5bc9cf04e89a < a15f37a40145c986cdf289a4b88390f35efdecc4`
- `Linux 5.18`

## Remediation

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