---
id: CVE-2025-21792
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ax25: Fix refcount leak caused by setting SO_BINDTODEVICE sockopt

  If an AX25 device is bound to a socket by setting the SO_BINDTODEVICE
  socket option, a refcount leak …
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ax25: Fix refcount leak caused by setting SO_BINDTODEVICE sockopt

  If an AX25 device is bound to a socket by setting the SO_BINDTODEVICE
  socket option, a refcount leak …
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 4.14.277, < 4.15'
  - 'linux_kernel >= 4.19.240, < 4.20'
  - 'linux_kernel >= 5.4.190, < 5.5'
  - 'linux_kernel >= 5.10.112, < 5.11'
  - 'linux_kernel >= 5.15.35, < 5.16'
  - 'linux_kernel >= 5.17.2, < 6.1.129'
  - 'linux_kernel >= 6.2, < 6.6.79'
  - 'linux_kernel >= 6.7, < 6.12.16'
  - 'linux_kernel >= 6.13, < 6.13.4'
  - linux_kernel = 6.14
patched:
  - linux_kernel 6.13.4
published: '2025-02-27'
updated: '2026-07-30'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-21792'
references:
  - url: 'https://git.kernel.org/stable/c/470bda72fda0fcf54300466d70ce2de62f7835d2'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/90056ece99966182dc0e367f3fd2afab46ada847'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/94a0de224ed52eb2ecd4f4cb1b937b674c9fb955'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/b58f7ca86a7b8e480c06e30c5163c5d2f4e24023'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/bca0902e61731a75fc4860c8720168d9f1bae3b6'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.00241
epssPercentile: 0.13564
ingestedAt: '2026-07-30T06:53:10.007Z'
---

## Overview

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

ax25: Fix refcount leak caused by setting SO_BINDTODEVICE sockopt

If an AX25 device is bound to a socket by setting the SO_BINDTODEVICE
socket option, a refcount leak will occur in ax25_release().

Commit 9fd75b66b8f6 ("ax25: Fix refcount leaks caused by ax25_cb_del()")
added decrement of device refcounts in ax25_release(). In order for that
to work correctly the refcounts must already be incremented when the
device is bound to the socket. An AX25 device can be bound to a socket
by either calling ax25_bind() or setting SO_BINDTODEVICE socket option.
In both cases the refcounts should be incremented, but in fact it is done
only in ax25_bind().

This bug leads to the following issue reported by Syzkaller:

================================================================
refcount_t: decrement hit 0; leaking memory.
WARNING: CPU: 1 PID: 5932 at lib/refcount.c:31 refcount_warn_saturate+0x1ed/0x210 lib/refcount.c:31
Modules linked in:
CPU: 1 UID: 0 PID: 5932 Comm: syz-executor424 Not tainted 6.13.0-rc4-syzkaller-00110-g4099a71718b0 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:refcount_warn_saturate+0x1ed/0x210 lib/refcount.c:31
Call Trace:
 <TASK>
 __refcount_dec include/linux/refcount.h:336 [inline]
 refcount_dec include/linux/refcount.h:351 [inline]
 ref_tracker_free+0x710/0x820 lib/ref_tracker.c:236
 netdev_tracker_free include/linux/netdevice.h:4156 [inline]
 netdev_put include/linux/netdevice.h:4173 [inline]
 netdev_put include/linux/netdevice.h:4169 [inline]
 ax25_release+0x33f/0xa10 net/ax25/af_ax25.c:1069
 __sock_release+0xb0/0x270 net/socket.c:640
 sock_close+0x1c/0x30 net/socket.c:1408
 ...
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
 ...
 </TASK>
================================================================

Fix the implementation of ax25_setsockopt() by adding increment of
refcounts for the new device bound, and decrement of refcounts for
the old unbound device.

## Affected

- `linux_kernel >= 4.14.277, < 4.15`
- `linux_kernel >= 4.19.240, < 4.20`
- `linux_kernel >= 5.4.190, < 5.5`
- `linux_kernel >= 5.10.112, < 5.11`
- `linux_kernel >= 5.15.35, < 5.16`
- `linux_kernel >= 5.17.2, < 6.1.129`
- `linux_kernel >= 6.2, < 6.6.79`
- `linux_kernel >= 6.7, < 6.12.16`
- `linux_kernel >= 6.13, < 6.13.4`
- `linux_kernel = 6.14`

## Remediation

Upgrade past the affected range:

- `linux_kernel 6.13.4`