Description
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.
Published: 2025-02-27
Score: 5.5 Medium
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

No vendor fix or workaround currently provided.

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Tracking

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Advisories
Source ID Title
Debian DLA Debian DLA DLA-4102-1 linux-6.1 security update
EUVD EUVD EUVD-2025-5128 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.
Ubuntu USN Ubuntu USN USN-7521-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-7521-2 Linux kernel (AWS) vulnerabilities
Ubuntu USN Ubuntu USN USN-7521-3 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-7703-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-7703-2 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-7703-3 Linux kernel (Oracle) vulnerabilities
Ubuntu USN Ubuntu USN USN-7703-4 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-7719-1 Linux kernel (Raspberry Pi Real-time) vulnerabilities
Ubuntu USN Ubuntu USN USN-7737-1 Linux kernel (Azure) vulnerabilities
History

Mon, 03 Nov 2025 21:30:00 +0000

Type Values Removed Values Added
References

Wed, 01 Oct 2025 20:30:00 +0000

Type Values Removed Values Added
First Time appeared Linux
Linux linux Kernel
Weaknesses NVD-CWE-Other
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.14:rc1:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.14:rc2:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel

Wed, 01 Oct 2025 20:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Mon, 17 Mar 2025 09:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-401

Fri, 28 Feb 2025 02:00:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

 cvssV3_1

{'score': 5.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

threat_severity

Moderate

Thu, 27 Feb 2025 02:45:00 +0000

Type Values Removed Values Added
Description 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.
Title ax25: Fix refcount leak caused by setting SO_BINDTODEVICE sockopt
References

Subscriptions

Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-05-11T21:06:35.276Z

Reserved: 2024-12-29T08:45:45.767Z

Link: CVE-2025-21792

cve-icon Vulnrichment

Updated: 2025-11-03T20:59:36.026Z

cve-icon NVD

Status : Modified

Published: 2025-02-27T03:15:20.080

Modified: 2025-11-03T21:19:10.457

Link: CVE-2025-21792

cve-icon Redhat

Severity : Moderate

Publid Date: 2025-02-27T00:00:00Z

Links: CVE-2025-21792 - Bugzilla

cve-icon OpenCVE Enrichment

No data.

Weaknesses