---
id: CVE-2026-43027
title: 'netfilter: nf_conntrack_helper: pass helper to expect cleanup'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  netfilter: nf_conntrack_helper: pass helper to expect cleanup

  nf_conntrack_helper_unregister() calls nf_ct_expect_iterate_destroy()
  to remove expectations belonging to…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= ac7b848390036dadd4351899d2a23748075916bd <
    5cf28d5c8dcbbe8af6d3b145babe491906d7bad1
  - >-
    Linux >= ac7b848390036dadd4351899d2a23748075916bd <
    504ba4168466c91210c45acdc332479cfd5f2da6
  - >-
    Linux >= ac7b848390036dadd4351899d2a23748075916bd <
    dc1739eff48e34cc71d4e2f03715493fbcebd8af
  - >-
    Linux >= ac7b848390036dadd4351899d2a23748075916bd <
    2cf2737c85a2ba2b52024dafe68ffad2676f97be
  - >-
    Linux >= ac7b848390036dadd4351899d2a23748075916bd <
    2c16e4d64dd91227742dfe196a3e7b0568bef65a
  - >-
    Linux >= ac7b848390036dadd4351899d2a23748075916bd <
    620f3d14c1ef51d425060a3056ad8dbae8f998a3
  - >-
    Linux >= ac7b848390036dadd4351899d2a23748075916bd <
    90bd7e8501349db3006d21fbc09df9ffcb172965
  - >-
    Linux >= ac7b848390036dadd4351899d2a23748075916bd <
    a242a9ae58aa46ff7dae51ce64150a93957abe65
  - Linux 4.14
published: '2026-05-01'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T08:48:27.805Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-43027'
references:
  - url: 'https://git.kernel.org/stable/c/5cf28d5c8dcbbe8af6d3b145babe491906d7bad1'
  - url: 'https://git.kernel.org/stable/c/504ba4168466c91210c45acdc332479cfd5f2da6'
  - url: 'https://git.kernel.org/stable/c/dc1739eff48e34cc71d4e2f03715493fbcebd8af'
  - url: 'https://git.kernel.org/stable/c/2cf2737c85a2ba2b52024dafe68ffad2676f97be'
  - url: 'https://git.kernel.org/stable/c/2c16e4d64dd91227742dfe196a3e7b0568bef65a'
  - url: 'https://git.kernel.org/stable/c/620f3d14c1ef51d425060a3056ad8dbae8f998a3'
  - url: 'https://git.kernel.org/stable/c/90bd7e8501349db3006d21fbc09df9ffcb172965'
  - url: 'https://git.kernel.org/stable/c/a242a9ae58aa46ff7dae51ce64150a93957abe65'
tags:
  - cve.org
epss: 0.00179
epssPercentile: 0.06564
ingestedAt: '2026-09-08T15:33:26.989Z'
---

## Overview

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

netfilter: nf_conntrack_helper: pass helper to expect cleanup

nf_conntrack_helper_unregister() calls nf_ct_expect_iterate_destroy()
to remove expectations belonging to the helper being unregistered.
However, it passes NULL instead of the helper pointer as the data
argument, so expect_iter_me() never matches any expectation and all
of them survive the cleanup.

After unregister returns, nfnl_cthelper_del() frees the helper
object immediately.  Subsequent expectation dumps or packet-driven
init_conntrack() calls then dereference the freed exp->helper,
causing a use-after-free.

Pass the actual helper pointer so expectations referencing it are
properly destroyed before the helper object is freed.

  BUG: KASAN: slab-use-after-free in string+0x38f/0x430
  Read of size 1 at addr ffff888003b14d20 by task poc/103
  Call Trace:
   string+0x38f/0x430
   vsnprintf+0x3cc/0x1170
   seq_printf+0x17a/0x240
   exp_seq_show+0x2e5/0x560
   seq_read_iter+0x419/0x1280
   proc_reg_read+0x1ac/0x270
   vfs_read+0x179/0x930
   ksys_read+0xef/0x1c0
  Freed by task 103:
  The buggy address is located 32 bytes inside of
   freed 192-byte region [ffff888003b14d00, ffff888003b14dc0)

## Affected

- `Linux >= ac7b848390036dadd4351899d2a23748075916bd < 5cf28d5c8dcbbe8af6d3b145babe491906d7bad1`
- `Linux >= ac7b848390036dadd4351899d2a23748075916bd < 504ba4168466c91210c45acdc332479cfd5f2da6`
- `Linux >= ac7b848390036dadd4351899d2a23748075916bd < dc1739eff48e34cc71d4e2f03715493fbcebd8af`
- `Linux >= ac7b848390036dadd4351899d2a23748075916bd < 2cf2737c85a2ba2b52024dafe68ffad2676f97be`
- `Linux >= ac7b848390036dadd4351899d2a23748075916bd < 2c16e4d64dd91227742dfe196a3e7b0568bef65a`
- `Linux >= ac7b848390036dadd4351899d2a23748075916bd < 620f3d14c1ef51d425060a3056ad8dbae8f998a3`
- `Linux >= ac7b848390036dadd4351899d2a23748075916bd < 90bd7e8501349db3006d21fbc09df9ffcb172965`
- `Linux >= ac7b848390036dadd4351899d2a23748075916bd < a242a9ae58aa46ff7dae51ce64150a93957abe65`
- `Linux 4.14`

## Remediation

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