---
id: CVE-2025-39764
title: 'netfilter: ctnetlink: remove refcounting in expectation dumpers'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  netfilter: ctnetlink: remove refcounting in expectation dumpers

  Same pattern as previous patch: do not keep the expectation object
  alive via refcount, only store a coo…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= cf6994c2b9812a9f02b99e89df411ffc5db9c779 <
    b05500444b8eb97644efdd180839a04a706be97c
  - >-
    Linux >= cf6994c2b9812a9f02b99e89df411ffc5db9c779 <
    bada48ad5b0590e318d0f79636ff62a2ef9f4955
  - >-
    Linux >= cf6994c2b9812a9f02b99e89df411ffc5db9c779 <
    64b7684042246e3238464c66894e30ba30c7e851
  - >-
    Linux >= cf6994c2b9812a9f02b99e89df411ffc5db9c779 <
    9e5021a906532ca16e2aac69c0607711e1c70b1f
  - >-
    Linux >= cf6994c2b9812a9f02b99e89df411ffc5db9c779 <
    078d33c95bf534d37aa04269d1ae6158e20082d5
  - >-
    Linux >= cf6994c2b9812a9f02b99e89df411ffc5db9c779 <
    a4d634ded4d3d400f115d84f654f316f249531c9
  - >-
    Linux >= cf6994c2b9812a9f02b99e89df411ffc5db9c779 <
    1492e3dcb2be3aa46d1963da96aa9593e4e4db5a
  - Linux 2.6.23
published: '2025-09-11'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T08:42:13.716Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2025-39764'
references:
  - url: 'https://git.kernel.org/stable/c/b05500444b8eb97644efdd180839a04a706be97c'
  - url: 'https://git.kernel.org/stable/c/bada48ad5b0590e318d0f79636ff62a2ef9f4955'
  - url: 'https://git.kernel.org/stable/c/64b7684042246e3238464c66894e30ba30c7e851'
  - url: 'https://git.kernel.org/stable/c/9e5021a906532ca16e2aac69c0607711e1c70b1f'
  - url: 'https://git.kernel.org/stable/c/078d33c95bf534d37aa04269d1ae6158e20082d5'
  - url: 'https://git.kernel.org/stable/c/a4d634ded4d3d400f115d84f654f316f249531c9'
  - url: 'https://git.kernel.org/stable/c/1492e3dcb2be3aa46d1963da96aa9593e4e4db5a'
tags:
  - cve.org
epss: 0.00165
epssPercentile: 0.06164
ingestedAt: '2026-09-08T15:33:26.997Z'
---

## Overview

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

netfilter: ctnetlink: remove refcounting in expectation dumpers

Same pattern as previous patch: do not keep the expectation object
alive via refcount, only store a cookie value and then use that
as the skip hint for dump resumption.

AFAICS this has the same issue as the one resolved in the conntrack
dumper, when we do
  if (!refcount_inc_not_zero(&exp->use))

to increment the refcount, there is a chance that exp == last, which
causes a double-increment of the refcount and subsequent memory leak.

## Affected

- `Linux >= cf6994c2b9812a9f02b99e89df411ffc5db9c779 < b05500444b8eb97644efdd180839a04a706be97c`
- `Linux >= cf6994c2b9812a9f02b99e89df411ffc5db9c779 < bada48ad5b0590e318d0f79636ff62a2ef9f4955`
- `Linux >= cf6994c2b9812a9f02b99e89df411ffc5db9c779 < 64b7684042246e3238464c66894e30ba30c7e851`
- `Linux >= cf6994c2b9812a9f02b99e89df411ffc5db9c779 < 9e5021a906532ca16e2aac69c0607711e1c70b1f`
- `Linux >= cf6994c2b9812a9f02b99e89df411ffc5db9c779 < 078d33c95bf534d37aa04269d1ae6158e20082d5`
- `Linux >= cf6994c2b9812a9f02b99e89df411ffc5db9c779 < a4d634ded4d3d400f115d84f654f316f249531c9`
- `Linux >= cf6994c2b9812a9f02b99e89df411ffc5db9c779 < 1492e3dcb2be3aa46d1963da96aa9593e4e4db5a`
- `Linux 2.6.23`

## Remediation

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