---
id: CVE-2026-97609
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  netfilter: cttimeout: prevent UAF during module unload

  nf_ct_set_timeout() protects the timeout hook dereference and policy lookup
  with rcu_read_lock()
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  netfilter: cttimeout: prevent UAF during module unload

  nf_ct_set_timeout() protects the timeout hook dereference and policy lookup
  with rcu_read_lock(). cttimeout_exit…
severity: high
cvss: 7
cvssVector: 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= ebfbe67568a734a449203097b02c4ab884257535 <
    a7fdd86c386b7f7cc72a126389c2cdb55d035221
  - >-
    Linux >= ebfbe67568a734a449203097b02c4ab884257535 <
    1f69c570a73f2dedf75ea5166d47622d5fa958c1
  - >-
    Linux >= ebfbe67568a734a449203097b02c4ab884257535 <
    fec9b1de0d02de8dafa3cc344bcb91cf28660643
  - Linux 5.13
published: '2026-09-25'
updated: '2026-09-25'
sourceUpdated: '2026-09-25T15:18:01.247'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-97609'
references:
  - url: 'https://git.kernel.org/stable/c/1f69c570a73f2dedf75ea5166d47622d5fa958c1'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/a7fdd86c386b7f7cc72a126389c2cdb55d035221'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/fec9b1de0d02de8dafa3cc344bcb91cf28660643'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-25T11:06:38.900Z'
---

## Overview

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

netfilter: cttimeout: prevent UAF during module unload

nf_ct_set_timeout() protects the timeout hook dereference and policy lookup
with rcu_read_lock(). cttimeout_exit(), however, unregisters the per-net
operations before it clears the hook.

This allows the following interleaving:

  CPU 0                              CPU 1
  cttimeout_exit()                   nf_ct_set_timeout()
    unregister_pernet_subsys()         rcu_read_lock()
      kfree(pernet)                     h = nf_ct_timeout_hook
                                        h->timeout_find_get()
                                          nfct_timeout_pernet()

The hook still points to ctnl_timeout_find_get() when CPU 1 looks up the
already freed per-net timeout list. KASAN reported:

  BUG: KASAN: slab-use-after-free in ctnl_timeout_find_get
  Read of size 8 by task poc/90
  Call Trace:
   ctnl_timeout_find_get+0x271/0x2a0 [nfnetlink_cttimeout]
   nf_ct_set_timeout+0x7b/0x3c0
   xt_ct_tg_check+0x724/0xb20
   xt_check_target+0x234/0xa90
   do_ipt_set_ctl+0x570/0x1270
  Allocated by task 89:
   __kmalloc_noprof+0x16e/0x460
   ops_init+0x6d/0x420
   register_pernet_operations+0x2f6/0x670
  Freed by task 91:
   kfree+0x131/0x390
   ops_undo_list+0x3d4/0x730
   unregister_pernet_operations+0x232/0x490
   unregister_pernet_subsys+0x1c/0x30
   cttimeout_exit+0x52/0x970 [nfnetlink_cttimeout]

Clear the hook and wait for existing readers before unregistering the
per-net operations. This blocks new policy lookups and ensures readers that
observed the hook finish before the per-net storage is freed.

## Remediation

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