---
id: CVE-2025-38732
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  netfilter: nf_reject: don't leak dst refcount for loopback packets

  recent patches to add a WARN() when replacing skb dst entry found an
  old bug:

  WARNING: include/linu…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  netfilter: nf_reject: don't leak dst refcount for loopback packets

  recent patches to add a WARN() when replacing skb dst entry found an
  old bug:

  WARNING: include/linu…
severity: medium
cvss: 5.5
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 5.9, < 5.10.241'
  - 'linux_kernel >= 5.11, < 5.15.190'
  - 'linux_kernel >= 5.16, < 6.1.149'
  - 'linux_kernel >= 6.2, < 6.6.103'
  - 'linux_kernel >= 6.7, < 6.12.44'
  - 'linux_kernel >= 6.13, < 6.16.4'
  - linux_kernel = 6.17
  - debian_linux = 11.0
patched:
  - linux_kernel 6.16.4
published: '2025-09-05'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T02:17:58.070'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-38732'
references:
  - url: 'https://git.kernel.org/stable/c/51e8531371f90bee742c63775c9a568e5d6bf3c5'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/7b8b503c06274ef3c6c1a107743f1ec0d0a53ef8'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/82ef97abf22790182f7d433c74960dfd61b99c33'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/91a79b792204313153e1bdbbe5acbfc28903b3a5'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/a0a3ace2a57887dac1e7c9a724846040c3e31868'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/b32e1590a8d22cf7d7f965e46d5576051acf8e42'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/b7a885ba25960c91db237c3f83b4285156789bce'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-019113.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-032379.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-457936.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
tags:
  - nvd
  - cve.org
epss: 0.00176
epssPercentile: 0.07041
ingestedAt: '2026-09-08T15:33:26.997Z'
---

## Overview

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

netfilter: nf_reject: don't leak dst refcount for loopback packets

recent patches to add a WARN() when replacing skb dst entry found an
old bug:

WARNING: include/linux/skbuff.h:1165 skb_dst_check_unset include/linux/skbuff.h:1164 [inline]
WARNING: include/linux/skbuff.h:1165 skb_dst_set include/linux/skbuff.h:1210 [inline]
WARNING: include/linux/skbuff.h:1165 nf_reject_fill_skb_dst+0x2a4/0x330 net/ipv4/netfilter/nf_reject_ipv4.c:234
[..]
Call Trace:
 nf_send_unreach+0x17b/0x6e0 net/ipv4/netfilter/nf_reject_ipv4.c:325
 nft_reject_inet_eval+0x4bc/0x690 net/netfilter/nft_reject_inet.c:27
 expr_call_ops_eval net/netfilter/nf_tables_core.c:237 [inline]
 ..

This is because blamed commit forgot about loopback packets.
Such packets already have a dst_entry attached, even at PRE_ROUTING stage.

Instead of checking hook just check if the skb already has a route
attached to it.

## Affected

- `linux_kernel >= 5.9, < 5.10.241`
- `linux_kernel >= 5.11, < 5.15.190`
- `linux_kernel >= 5.16, < 6.1.149`
- `linux_kernel >= 6.2, < 6.6.103`
- `linux_kernel >= 6.7, < 6.12.44`
- `linux_kernel >= 6.13, < 6.16.4`
- `linux_kernel = 6.17`
- `debian_linux = 11.0`

## Remediation

Upgrade past the affected range:

- `linux_kernel 6.16.4`