---
id: CVE-2026-74561
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  nexthop: avoid unlocked f6i_list walk in nh_rt_cache_flush

  nh_rt_cache_flush() walks nh->f6i_list during an RTNL-serialized nexthop
  replace without holding nh->lock, r…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  nexthop: avoid unlocked f6i_list walk in nh_rt_cache_flush

  nh_rt_cache_flush() walks nh->f6i_list during an RTNL-serialized nexthop
  replace without holding nh->lock, r…
severity: high
cvss: 8.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H'
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 081efd18326e353c6fbfdeff903a83edde953f72 <
    f97fae992155b11da516a509c855ff9d0868b107
  - >-
    Linux >= 081efd18326e353c6fbfdeff903a83edde953f72 <
    44f53e4331a30fabc38a411fae7524341b618db3
  - >-
    Linux >= 081efd18326e353c6fbfdeff903a83edde953f72 <
    4787a6d2629b4e8c0b6bacab1f75c1660eca44d9
  - Linux 6.16
published: '2026-08-15'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T11:17:47.580'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-74561'
references:
  - url: 'https://git.kernel.org/stable/c/44f53e4331a30fabc38a411fae7524341b618db3'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/4787a6d2629b4e8c0b6bacab1f75c1660eca44d9'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/f97fae992155b11da516a509c855ff9d0868b107'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
epss: 0.00165
epssPercentile: 0.05325
ingestedAt: '2026-10-15T11:00:41.671Z'
---

## Overview

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

nexthop: avoid unlocked f6i_list walk in nh_rt_cache_flush

nh_rt_cache_flush() walks nh->f6i_list during an RTNL-serialized nexthop
replace without holding nh->lock, racing the unlocked IPv6 route
add/delete that mutate the list under nh->lock and free fib6_info
entries (nh_rt_cache_flush() is inlined into rtm_new_nexthop()):

  BUG: KASAN: slab-use-after-free in nh_rt_cache_flush (net/ipv4/nexthop.c:2243)
  Read of size 8 at addr ffff888012953e18 by task exploit/146
   nh_rt_cache_flush (net/ipv4/nexthop.c:2243)
   replace_nexthop (net/ipv4/nexthop.c:2610)
   rtm_new_nexthop (net/ipv4/nexthop.c:3323)
   rtnetlink_rcv_msg (net/core/rtnetlink.c:7076)

Unlike the other f6i_list walks, this one bumps each route's sernum via
fib6_update_sernum_upto_root(), which needs tb6_lock; taking nh->lock
around it would invert the established tb6_lock -> nh->lock order and
deadlock. As the only purpose is to invalidate cached dsts, bump the
IPv6 sernum for the whole netns with rt_genid_bump_ipv6() instead,
mirroring the rt_cache_flush() already done for IPv4 just above.

## Remediation

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