---
id: CVE-2025-21765
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ipv6: use RCU protection in ip6_default_advmss()

  ip6_default_advmss() needs rcu protection to make
  sure the net structure it reads does not disappear.
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ipv6: use RCU protection in ip6_default_advmss()

  ip6_default_advmss() needs rcu protection to make
  sure the net structure it reads does not disappear.
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'
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 2.6.26, < 5.4.291'
  - 'linux_kernel >= 5.5, < 5.10.235'
  - 'linux_kernel >= 5.11, < 5.15.179'
  - 'linux_kernel >= 5.16, < 6.1.129'
  - 'linux_kernel >= 6.2, < 6.6.79'
  - 'linux_kernel >= 6.7, < 6.12.16'
  - 'linux_kernel >= 6.13, < 6.13.4'
  - linux_kernel = 6.14
patched:
  - linux_kernel 6.13.4
published: '2025-02-27'
updated: '2026-07-14'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-21765'
references:
  - url: 'https://git.kernel.org/stable/c/28de355b63ad42309ed5a03ee7c436c90512265b'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/3c8ffcd248da34fc41e52a46e51505900115fc2a'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/4176a68b0db8fc74ac14fcd00ba8231371051dc2'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/550ed693f47370502a71b85382e7f9e6417300b8'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/713a40c892f40300d63691d9f85b2a23b48fe1e8'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/78ad057472d8c76e0602402269222f9f9c698790'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/84212387caadb211cd9dadd6fd5563bd37dc1f5e'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/d02f30d220ef9511568a48dba8a9004c65f8d904'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-019113.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-082556.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-265688.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
tags:
  - nvd
  - cve.org
epss: 0.00613
epssPercentile: 0.47129
ingestedAt: '2026-07-14T13:36:55.697Z'
---

## Overview

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

ipv6: use RCU protection in ip6_default_advmss()

ip6_default_advmss() needs rcu protection to make
sure the net structure it reads does not disappear.

## Affected

- `linux_kernel >= 2.6.26, < 5.4.291`
- `linux_kernel >= 5.5, < 5.10.235`
- `linux_kernel >= 5.11, < 5.15.179`
- `linux_kernel >= 5.16, < 6.1.129`
- `linux_kernel >= 6.2, < 6.6.79`
- `linux_kernel >= 6.7, < 6.12.16`
- `linux_kernel >= 6.13, < 6.13.4`
- `linux_kernel = 6.14`

## Remediation

Upgrade past the affected range:

- `linux_kernel 6.13.4`