---
id: CVE-2025-21768
title: 'net: ipv6: fix dst ref loops in rpl, seg6 and ioam6 lwtunnels'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net: ipv6: fix dst ref loops in rpl, seg6 and ioam6 lwtunnels

  Some lwtunnels have a dst cache for post-transformation dst.
  If the packet destination did not change we …
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 6c8702c60b88651072460f3f4026c7dfe2521d12 <
    e2ef3fa31353b30bda94358fe5205c141289746d
  - >-
    Linux >= 6c8702c60b88651072460f3f4026c7dfe2521d12 <
    5ab11a4e219e93b8b31a27f8ec98d42afadd8b7a
  - >-
    Linux >= 6c8702c60b88651072460f3f4026c7dfe2521d12 <
    4c0f200c7d06fedddde82209c099014d63f4a6c0
  - >-
    Linux >= 6c8702c60b88651072460f3f4026c7dfe2521d12 <
    92191dd1073088753821b862b791dcc83e558e07
  - Linux 4.10
published: '2025-02-27'
updated: '2026-10-21'
sourceUpdated: '2026-10-21T12:35:59.286Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2025-21768'
references:
  - url: 'https://git.kernel.org/stable/c/e2ef3fa31353b30bda94358fe5205c141289746d'
  - url: 'https://git.kernel.org/stable/c/5ab11a4e219e93b8b31a27f8ec98d42afadd8b7a'
  - url: 'https://git.kernel.org/stable/c/4c0f200c7d06fedddde82209c099014d63f4a6c0'
  - url: 'https://git.kernel.org/stable/c/92191dd1073088753821b862b791dcc83e558e07'
tags:
  - cve.org
epss: 0.00254
epssPercentile: 0.16809
ingestedAt: '2026-10-21T12:48:53.718Z'
---

## Overview

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

net: ipv6: fix dst ref loops in rpl, seg6 and ioam6 lwtunnels

Some lwtunnels have a dst cache for post-transformation dst.
If the packet destination did not change we may end up recording
a reference to the lwtunnel in its own cache, and the lwtunnel
state will never be freed.

Discovered by the ioam6.sh test, kmemleak was recently fixed
to catch per-cpu memory leaks. I'm not sure if rpl and seg6
can actually hit this, but in principle I don't see why not.

## Affected

- `Linux >= 6c8702c60b88651072460f3f4026c7dfe2521d12 < e2ef3fa31353b30bda94358fe5205c141289746d`
- `Linux >= 6c8702c60b88651072460f3f4026c7dfe2521d12 < 5ab11a4e219e93b8b31a27f8ec98d42afadd8b7a`
- `Linux >= 6c8702c60b88651072460f3f4026c7dfe2521d12 < 4c0f200c7d06fedddde82209c099014d63f4a6c0`
- `Linux >= 6c8702c60b88651072460f3f4026c7dfe2521d12 < 92191dd1073088753821b862b791dcc83e558e07`
- `Linux 4.10`

## Remediation

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