---
id: CVE-2025-21640
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  sctp: sysctl: cookie_hmac_alg: avoid using current->nsproxy

  As mentioned in a previous commit of this series, using the 'net'
  structure via 'current' is not recommende…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  sctp: sysctl: cookie_hmac_alg: avoid using current->nsproxy

  As mentioned in a previous commit of this series, using the 'net'
  structure via 'current' is not recommende…
severity: high
cvss: 7.1
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H'
cwe:
  - CWE-476
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 3.8, < 6.1.125'
  - 'linux_kernel >= 6.2, < 6.6.72'
  - 'linux_kernel >= 6.7, < 6.12.10'
  - linux_kernel = 6.13
patched:
  - linux_kernel 6.12.10
published: '2025-01-19'
updated: '2026-07-30'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-21640'
references:
  - url: 'https://git.kernel.org/stable/c/03ca51faba2b017bf6c90e139434c4117d0afcdc'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/3cd0659deb9c03535fd61839e91d4d4d3e51ac71'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/5599b212d2f4466e1832a94e9932684aaa364587'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/86ddf8118123cb58a0fb8724cad6979c4069065b'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/ad673e514b2793b8d5902f6ba6ab7e890dea23d5'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/ea62dd1383913b5999f3d16ae99d411f41b528d4'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/f0bb3935470684306e4e04793a20ac4c4b08de0b'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://lists.debian.org/debian-lts-announce/2025/03/msg00001.html'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://lists.debian.org/debian-lts-announce/2025/03/msg00002.html'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-265688.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
tags:
  - nvd
epss: 0.00237
epssPercentile: 0.13027
ingestedAt: '2026-07-30T06:53:08.880Z'
---

## Overview

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

sctp: sysctl: cookie_hmac_alg: avoid using current->nsproxy

As mentioned in a previous commit of this series, using the 'net'
structure via 'current' is not recommended for different reasons:

- Inconsistency: getting info from the reader's/writer's netns vs only
  from the opener's netns.

- current->nsproxy can be NULL in some cases, resulting in an 'Oops'
  (null-ptr-deref), e.g. when the current task is exiting, as spotted by
  syzbot [1] using acct(2).

The 'net' structure can be obtained from the table->data using
container_of().

Note that table->data could also be used directly, as this is the only
member needed from the 'net' structure, but that would increase the size
of this fix, to use '*data' everywhere 'net->sctp.sctp_hmac_alg' is
used.

## Affected

- `linux_kernel >= 3.8, < 6.1.125`
- `linux_kernel >= 6.2, < 6.6.72`
- `linux_kernel >= 6.7, < 6.12.10`
- `linux_kernel = 6.13`

## Remediation

Upgrade past the affected range:

- `linux_kernel 6.12.10`