---
id: CVE-2026-63968
title: 'ipv6: fix possible infinite loop in fib6_select_path()'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ipv6: fix possible infinite loop in fib6_select_path()

  Found while auditing the same pattern Sashiko reported in
  rt6_fill_node() [1]. Apply the same fix as
  commit f8d8…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= d0ec61c9f3583b76aebdbb271f5c0d3fcccd48b2 <
    3948a7d92f7678e89e1776bb2d169afcad63b1ae
  - >-
    Linux >= 52da02521ede55fb86546c3fffd9377b3261b91f <
    c87cd3cb309634bc8f50a54e2079424f219ac21f
  - >-
    Linux >= 34a949e7a0869dfa31a40416d2a56973fae1807b <
    0f7b73c3452635de83b8711b31abdda8e49aad7b
  - >-
    Linux >= d9ccb18f83ea2bb654289b6ecf014fd267cc988b <
    ab9a10969a907b472a0196d999c08ff7144172e3
  - >-
    Linux >= d9ccb18f83ea2bb654289b6ecf014fd267cc988b <
    9b9d5bd6e3d4c9cecab5407604b690684b2532d2
  - >-
    Linux >= d9ccb18f83ea2bb654289b6ecf014fd267cc988b <
    9c7da87c2dc860bb17ca1ece942495d28b1ce3b9
  - Linux 11edcd026012ac18acee0f1514db3ed1b160fc6f
  - Linux >= 6.1.128 < 6.1.176
  - Linux >= 6.6.75 < 6.6.143
  - Linux >= 6.12.2 < 6.12.93
  - Linux >= 6.11.11 < 6.12
  - Linux 6.13
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-10-16T15:34:13.232918Z'
published: '2026-07-19'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T15:42:14.683Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-63968'
references:
  - url: 'https://git.kernel.org/stable/c/3948a7d92f7678e89e1776bb2d169afcad63b1ae'
  - url: 'https://git.kernel.org/stable/c/c87cd3cb309634bc8f50a54e2079424f219ac21f'
  - url: 'https://git.kernel.org/stable/c/0f7b73c3452635de83b8711b31abdda8e49aad7b'
  - url: 'https://git.kernel.org/stable/c/ab9a10969a907b472a0196d999c08ff7144172e3'
  - url: 'https://git.kernel.org/stable/c/9b9d5bd6e3d4c9cecab5407604b690684b2532d2'
  - url: 'https://git.kernel.org/stable/c/9c7da87c2dc860bb17ca1ece942495d28b1ce3b9'
tags:
  - cve.org
epss: 0.00665
epssPercentile: 0.50747
ingestedAt: '2026-10-16T17:24:46.784Z'
---

## Overview

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

ipv6: fix possible infinite loop in fib6_select_path()

Found while auditing the same pattern Sashiko reported in
rt6_fill_node() [1]. Apply the same fix as
commit f8d8ce1b515a ("ipv6: fix possible infinite loop in fib6_info_uses_dev()").

Writers holding tb6_lock can list_del_rcu(&first->fib6_siblings)
without waiting for RCU readers; first->fib6_siblings.next then
still points into the old ring and this softirq-side walker never
reaches &first->fib6_siblings as its terminator. fib6_purge_rt()
always WRITE_ONCE()s first->fib6_nsiblings to 0 before
list_del_rcu(), so an inside-loop check is a reliable detach signal.

[1] https://sashiko.dev/#/patchset/20260526020227.4857-1-jiayuan.chen%40linux.dev

## Affected

- `Linux >= d0ec61c9f3583b76aebdbb271f5c0d3fcccd48b2 < 3948a7d92f7678e89e1776bb2d169afcad63b1ae`
- `Linux >= 52da02521ede55fb86546c3fffd9377b3261b91f < c87cd3cb309634bc8f50a54e2079424f219ac21f`
- `Linux >= 34a949e7a0869dfa31a40416d2a56973fae1807b < 0f7b73c3452635de83b8711b31abdda8e49aad7b`
- `Linux >= d9ccb18f83ea2bb654289b6ecf014fd267cc988b < ab9a10969a907b472a0196d999c08ff7144172e3`
- `Linux >= d9ccb18f83ea2bb654289b6ecf014fd267cc988b < 9b9d5bd6e3d4c9cecab5407604b690684b2532d2`
- `Linux >= d9ccb18f83ea2bb654289b6ecf014fd267cc988b < 9c7da87c2dc860bb17ca1ece942495d28b1ce3b9`
- `Linux 11edcd026012ac18acee0f1514db3ed1b160fc6f`
- `Linux >= 6.1.128 < 6.1.176`
- `Linux >= 6.6.75 < 6.6.143`
- `Linux >= 6.12.2 < 6.12.93`
- `Linux >= 6.11.11 < 6.12`
- `Linux 6.13`

## Remediation

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