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.

The remote Debian 11 host has packages installed that are affected by multiple vulnerabilities as referenced in the dla-4102 advisory.

    -------------------------------------------------------------------------     Debian LTS Advisory DLA-4102-1                debian-lts@lists.debian.org     https://www.debian.org/lts/security/                        Ben Hutchings     March 31, 2025                                https://wiki.debian.org/LTS
    -------------------------------------------------------------------------

    Package        : linux-6.1     Version        : 6.1.129-1~deb11u1     CVE ID         : CVE-2024-26596 CVE-2024-40945 CVE-2024-42069 CVE-2024-42122                      CVE-2024-45001 CVE-2024-47726 CVE-2024-49989 CVE-2024-50061                      CVE-2024-54458 CVE-2024-56549 CVE-2024-57834 CVE-2024-57973                      CVE-2024-57978 CVE-2024-57979 CVE-2024-57980 CVE-2024-57981                      CVE-2024-57986 CVE-2024-57993 CVE-2024-57996 CVE-2024-57997                      CVE-2024-57998 CVE-2024-58001 CVE-2024-58007 CVE-2024-58009                      CVE-2024-58010 CVE-2024-58011 CVE-2024-58013 CVE-2024-58014                      CVE-2024-58016 CVE-2024-58017 CVE-2024-58020 CVE-2024-58034                      CVE-2024-58051 CVE-2024-58052 CVE-2024-58054 CVE-2024-58055                      CVE-2024-58056 CVE-2024-58058 CVE-2024-58061 CVE-2024-58063                      CVE-2024-58068 CVE-2024-58069 CVE-2024-58071 CVE-2024-58072                      CVE-2024-58076 CVE-2024-58077 CVE-2024-58080 CVE-2024-58083                      CVE-2024-58085 CVE-2024-58086 CVE-2025-21684 CVE-2025-21700                      CVE-2025-21701 CVE-2025-21703 CVE-2025-21704 CVE-2025-21705                      CVE-2025-21706 CVE-2025-21707 CVE-2025-21708 CVE-2025-21711                      CVE-2025-21715 CVE-2025-21716 CVE-2025-21718 CVE-2025-21719                      CVE-2025-21722 CVE-2025-21724 CVE-2025-21725 CVE-2025-21726                      CVE-2025-21727 CVE-2025-21728 CVE-2025-21731 CVE-2025-21734                      CVE-2025-21735 CVE-2025-21736 CVE-2025-21738 CVE-2025-21744                      CVE-2025-21745 CVE-2025-21748 CVE-2025-21749 CVE-2025-21750                      CVE-2025-21753 CVE-2025-21758 CVE-2025-21760 CVE-2025-21761                      CVE-2025-21762 CVE-2025-21763 CVE-2025-21764 CVE-2025-21765                      CVE-2025-21766 CVE-2025-21767 CVE-2025-21772 CVE-2025-21775                      CVE-2025-21776 CVE-2025-21779 CVE-2025-21780 CVE-2025-21781                      CVE-2025-21782 CVE-2025-21785 CVE-2025-21787 CVE-2025-21790                      CVE-2025-21791 CVE-2025-21792 CVE-2025-21794 CVE-2025-21795                      CVE-2025-21796 CVE-2025-21799 CVE-2025-21802 CVE-2025-21804                      CVE-2025-21806 CVE-2025-21811 CVE-2025-21812 CVE-2025-21814                      CVE-2025-21819 CVE-2025-21820 CVE-2025-21821 CVE-2025-21823                      CVE-2025-21826 CVE-2025-21829 CVE-2025-21830 CVE-2025-21832                      CVE-2025-21835     Debian Bug     : 1071562 1087807 1088159 1091517 1091858 1093371 1095435                      1095745 1095764 1098250 1098354 1099138

    Several vulnerabilities have been discovered in the Linux kernel that     may lead to a privilege escalation, denial of service or information     leaks.

    For Debian 11 bullseye, these problems have been fixed in version     6.1.129-1~deb11u1.  This additionally includes many more bug fixes     from stable update 6.1.129, and a fix for a regression affecting some     Rockchip SoCs.

    We recommend that you upgrade your linux-6.1 packages.

    For the detailed security status of linux-6.1 please refer to     its security tracker page at:
    https://security-tracker.debian.org/tracker/linux-6.1

    Further information about Debian LTS security advisories, how to apply     these updates to your system and frequently asked questions can be     found at: https://wiki.debian.org/LTS     Attachment:
    signature.asc     Description: PGP signature

Tenable has extracted the preceding description block directly from the Debian security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - 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. (CVE-2025-21792)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Severity
233595	Debian dla-4102 : linux-config-6.1 - security update	Nessus	Debian Local Security Checks	high
230879	Linux Distros Unpatched Vulnerability : CVE-2025-21792	Nessus	Misc.	medium

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