---
id: CVE-2025-21639
title: 'sctp: sysctl: rto_min/max: avoid using current->nsproxy'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  sctp: sysctl: rto_min/max: avoid using current->nsproxy

  As mentioned in a previous commit of this series, using the 'net'
  structure via 'current' is not recommended fo…
severity: medium
cvss: 5.5
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'
cvssSource: adp
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 4f3fdf3bc59cafd14c3bc2c2369efad34c7aa8b5 <
    c8d179f3b1c1d60bf4484f50aa67b4c70f91bff9
  - >-
    Linux >= 4f3fdf3bc59cafd14c3bc2c2369efad34c7aa8b5 <
    246428bfb9e7db15c5cd08e1d0eca41b65af2b06
  - >-
    Linux >= 4f3fdf3bc59cafd14c3bc2c2369efad34c7aa8b5 <
    0f78f09466744589e420935e646ae78212a38290
  - >-
    Linux >= 4f3fdf3bc59cafd14c3bc2c2369efad34c7aa8b5 <
    4059507e34aa5fe0fa9fd5b2b5f0c8b26ab2d482
  - >-
    Linux >= 4f3fdf3bc59cafd14c3bc2c2369efad34c7aa8b5 <
    dc9d0e3cfd16f66fbf0862857c6b391c8613ca9f
  - >-
    Linux >= 4f3fdf3bc59cafd14c3bc2c2369efad34c7aa8b5 <
    c87f1f6ade56c711f8736901e330685b453e420e
  - >-
    Linux >= 4f3fdf3bc59cafd14c3bc2c2369efad34c7aa8b5 <
    9fc17b76fc70763780aa78b38fcf4742384044a5
  - Linux 3.13
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2025-10-01T19:54:07.301315Z'
published: '2025-01-19'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T01:02:42.114Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2025-21639'
references:
  - url: 'https://git.kernel.org/stable/c/c8d179f3b1c1d60bf4484f50aa67b4c70f91bff9'
  - url: 'https://git.kernel.org/stable/c/246428bfb9e7db15c5cd08e1d0eca41b65af2b06'
  - url: 'https://git.kernel.org/stable/c/0f78f09466744589e420935e646ae78212a38290'
  - url: 'https://git.kernel.org/stable/c/4059507e34aa5fe0fa9fd5b2b5f0c8b26ab2d482'
  - url: 'https://git.kernel.org/stable/c/dc9d0e3cfd16f66fbf0862857c6b391c8613ca9f'
  - url: 'https://git.kernel.org/stable/c/c87f1f6ade56c711f8736901e330685b453e420e'
  - url: 'https://git.kernel.org/stable/c/9fc17b76fc70763780aa78b38fcf4742384044a5'
tags:
  - cve.org
epss: 0.00229
epssPercentile: 0.13594
ingestedAt: '2026-10-15T04:46:37.352Z'
---

## Overview

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

sctp: sysctl: rto_min/max: 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.rto_min/max' is used.

## Affected

- `Linux >= 4f3fdf3bc59cafd14c3bc2c2369efad34c7aa8b5 < c8d179f3b1c1d60bf4484f50aa67b4c70f91bff9`
- `Linux >= 4f3fdf3bc59cafd14c3bc2c2369efad34c7aa8b5 < 246428bfb9e7db15c5cd08e1d0eca41b65af2b06`
- `Linux >= 4f3fdf3bc59cafd14c3bc2c2369efad34c7aa8b5 < 0f78f09466744589e420935e646ae78212a38290`
- `Linux >= 4f3fdf3bc59cafd14c3bc2c2369efad34c7aa8b5 < 4059507e34aa5fe0fa9fd5b2b5f0c8b26ab2d482`
- `Linux >= 4f3fdf3bc59cafd14c3bc2c2369efad34c7aa8b5 < dc9d0e3cfd16f66fbf0862857c6b391c8613ca9f`
- `Linux >= 4f3fdf3bc59cafd14c3bc2c2369efad34c7aa8b5 < c87f1f6ade56c711f8736901e330685b453e420e`
- `Linux >= 4f3fdf3bc59cafd14c3bc2c2369efad34c7aa8b5 < 9fc17b76fc70763780aa78b38fcf4742384044a5`
- `Linux 3.13`

## Remediation

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