---
id: CVE-2025-38732
title: 'netfilter: nf_reject: don''t leak dst refcount for loopback packets'
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: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= f53b9b0bdc59c0823679f2e3214e0d538f5951b9 <
    7b8b503c06274ef3c6c1a107743f1ec0d0a53ef8
  - >-
    Linux >= f53b9b0bdc59c0823679f2e3214e0d538f5951b9 <
    82ef97abf22790182f7d433c74960dfd61b99c33
  - >-
    Linux >= f53b9b0bdc59c0823679f2e3214e0d538f5951b9 <
    b7a885ba25960c91db237c3f83b4285156789bce
  - >-
    Linux >= f53b9b0bdc59c0823679f2e3214e0d538f5951b9 <
    a0a3ace2a57887dac1e7c9a724846040c3e31868
  - >-
    Linux >= f53b9b0bdc59c0823679f2e3214e0d538f5951b9 <
    51e8531371f90bee742c63775c9a568e5d6bf3c5
  - >-
    Linux >= f53b9b0bdc59c0823679f2e3214e0d538f5951b9 <
    b32e1590a8d22cf7d7f965e46d5576051acf8e42
  - >-
    Linux >= f53b9b0bdc59c0823679f2e3214e0d538f5951b9 <
    91a79b792204313153e1bdbbe5acbfc28903b3a5
  - Linux 5.9
published: '2025-09-05'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T08:42:03.055Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2025-38732'
references:
  - url: 'https://git.kernel.org/stable/c/7b8b503c06274ef3c6c1a107743f1ec0d0a53ef8'
  - url: 'https://git.kernel.org/stable/c/82ef97abf22790182f7d433c74960dfd61b99c33'
  - url: 'https://git.kernel.org/stable/c/b7a885ba25960c91db237c3f83b4285156789bce'
  - url: 'https://git.kernel.org/stable/c/a0a3ace2a57887dac1e7c9a724846040c3e31868'
  - url: 'https://git.kernel.org/stable/c/51e8531371f90bee742c63775c9a568e5d6bf3c5'
  - url: 'https://git.kernel.org/stable/c/b32e1590a8d22cf7d7f965e46d5576051acf8e42'
  - url: 'https://git.kernel.org/stable/c/91a79b792204313153e1bdbbe5acbfc28903b3a5'
tags:
  - cve.org
epss: 0.00172
epssPercentile: 0.05761
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 >= f53b9b0bdc59c0823679f2e3214e0d538f5951b9 < 7b8b503c06274ef3c6c1a107743f1ec0d0a53ef8`
- `Linux >= f53b9b0bdc59c0823679f2e3214e0d538f5951b9 < 82ef97abf22790182f7d433c74960dfd61b99c33`
- `Linux >= f53b9b0bdc59c0823679f2e3214e0d538f5951b9 < b7a885ba25960c91db237c3f83b4285156789bce`
- `Linux >= f53b9b0bdc59c0823679f2e3214e0d538f5951b9 < a0a3ace2a57887dac1e7c9a724846040c3e31868`
- `Linux >= f53b9b0bdc59c0823679f2e3214e0d538f5951b9 < 51e8531371f90bee742c63775c9a568e5d6bf3c5`
- `Linux >= f53b9b0bdc59c0823679f2e3214e0d538f5951b9 < b32e1590a8d22cf7d7f965e46d5576051acf8e42`
- `Linux >= f53b9b0bdc59c0823679f2e3214e0d538f5951b9 < 91a79b792204313153e1bdbbe5acbfc28903b3a5`
- `Linux 5.9`

## Remediation

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