{
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    "cveMetadata": {
        "cveId": "CVE-2024-36009",
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "state": "PUBLISHED",
        "assignerShortName": "Linux",
        "dateReserved": "2024-05-17T13:50:33.152Z",
        "datePublished": "2024-05-20T09:48:08.238Z",
        "dateUpdated": "2026-08-05T11:31:33.867Z"
    },
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        "cna": {
            "providerMetadata": {
                "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
                "shortName": "Linux",
                "dateUpdated": "2026-08-05T11:31:33.867Z"
            },
            "descriptions": [
                {
                    "lang": "en",
                    "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nax25: Fix netdev refcount issue\n\nThe dev_tracker is added to ax25_cb in ax25_bind(). When the\nax25 device is detaching, the dev_tracker of ax25_cb should be\ndeallocated in ax25_kill_by_device() instead of the dev_tracker\nof ax25_dev. The log reported by ref_tracker is shown below:\n\n[   80.884935] ref_tracker: reference already released.\n[   80.885150] ref_tracker: allocated in:\n[   80.885349]  ax25_dev_device_up+0x105/0x540\n[   80.885730]  ax25_device_event+0xa4/0x420\n[   80.885730]  notifier_call_chain+0xc9/0x1e0\n[   80.885730]  __dev_notify_flags+0x138/0x280\n[   80.885730]  dev_change_flags+0xd7/0x180\n[   80.885730]  dev_ifsioc+0x6a9/0xa30\n[   80.885730]  dev_ioctl+0x4d8/0xd90\n[   80.885730]  sock_do_ioctl+0x1c2/0x2d0\n[   80.885730]  sock_ioctl+0x38b/0x4f0\n[   80.885730]  __se_sys_ioctl+0xad/0xf0\n[   80.885730]  do_syscall_64+0xc4/0x1b0\n[   80.885730]  entry_SYSCALL_64_after_hwframe+0x67/0x6f\n[   80.885730] ref_tracker: freed in:\n[   80.885730]  ax25_device_event+0x272/0x420\n[   80.885730]  notifier_call_chain+0xc9/0x1e0\n[   80.885730]  dev_close_many+0x272/0x370\n[   80.885730]  unregister_netdevice_many_notify+0x3b5/0x1180\n[   80.885730]  unregister_netdev+0xcf/0x120\n[   80.885730]  sixpack_close+0x11f/0x1b0\n[   80.885730]  tty_ldisc_kill+0xcb/0x190\n[   80.885730]  tty_ldisc_hangup+0x338/0x3d0\n[   80.885730]  __tty_hangup+0x504/0x740\n[   80.885730]  tty_release+0x46e/0xd80\n[   80.885730]  __fput+0x37f/0x770\n[   80.885730]  __x64_sys_close+0x7b/0xb0\n[   80.885730]  do_syscall_64+0xc4/0x1b0\n[   80.885730]  entry_SYSCALL_64_after_hwframe+0x67/0x6f\n[   80.893739] ------------[ cut here ]------------\n[   80.894030] WARNING: CPU: 2 PID: 140 at lib/ref_tracker.c:255 ref_tracker_free+0x47b/0x6b0\n[   80.894297] Modules linked in:\n[   80.894929] CPU: 2 PID: 140 Comm: ax25_conn_rel_6 Not tainted 6.9.0-rc4-g8cd26fd90c1a #11\n[   80.895190] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qem4\n[   80.895514] RIP: 0010:ref_tracker_free+0x47b/0x6b0\n[   80.895808] Code: 83 c5 18 4c 89 eb 48 c1 eb 03 8a 04 13 84 c0 0f 85 df 01 00 00 41 83 7d 00 00 75 4b 4c 89 ff 9\n[   80.896171] RSP: 0018:ffff888009edf8c0 EFLAGS: 00000286\n[   80.896339] RAX: 1ffff1100141ac00 RBX: 1ffff1100149463b RCX: dffffc0000000000\n[   80.896502] RDX: 0000000000000001 RSI: 0000000000000246 RDI: ffff88800a0d6518\n[   80.896925] RBP: ffff888009edf9b0 R08: ffff88806d3288d3 R09: 1ffff1100da6511a\n[   80.897212] R10: dffffc0000000000 R11: ffffed100da6511b R12: ffff88800a4a31d4\n[   80.897859] R13: ffff88800a4a31d8 R14: dffffc0000000000 R15: ffff88800a0d6518\n[   80.898279] FS:  00007fd88b7fe700(0000) GS:ffff88806d300000(0000) knlGS:0000000000000000\n[   80.899436] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n[   80.900181] CR2: 00007fd88c001d48 CR3: 000000000993e000 CR4: 00000000000006f0\n...\n[   80.935774] ref_tracker: sp%d@000000000bb9df3d has 1/1 users at\n[   80.935774]      ax25_bind+0x424/0x4e0\n[   80.935774]      __sys_bind+0x1d9/0x270\n[   80.935774]      __x64_sys_bind+0x75/0x80\n[   80.935774]      do_syscall_64+0xc4/0x1b0\n[   80.935774]      entry_SYSCALL_64_after_hwframe+0x67/0x6f\n\nChange ax25_dev->dev_tracker to the dev_tracker of ax25_cb\nin order to mitigate the bug."
                }
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                    "cvssV3_1": {
                        "version": "3.1",
                        "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                        "baseScore": 7.8,
                        "baseSeverity": "HIGH"
                    },
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                        {
                            "lang": "en",
                            "value": "AV:L - The vulnerable path is reached through local syscalls — socket()/bind() on AF_AX25 plus the netdev down/unregister notifier — and AX.25 sockets and devices are restricted to the initial network namespace, so no remote or adjacent packet path reaches this code.\nAC:L - Within an affected configuration the erroneous tracker release is deterministic: any socket bound to the AX.25 device makes ax25_kill_by_device() free the wrong tracker, and the subsequent ax25_dev_device_down() double-free is unconditional. The heap-recycling escalation is driven by attacker-controlled AX.25 bind/close churn on both sides, so no condition outside the attacker's influence is required.\nPR:L - An ordinary unprivileged local user can create and bind an AX.25 socket (ax25_create requires no capability for SOCK_SEQPACKET/SOCK_DGRAM and ax25_bind only checks CAP_NET_ADMIN when the non-default ax25_uid_policy is set), and that bound socket is the precondition that makes the buggy netdev_put() execute.\nUI:N - No victim action is needed for the exploit itself — the trigger is the interface going down or the KISS/6pack TNC detaching, which happens as routine operation of an AX.25 station rather than as a deliberate user action on the attacker's behalf.\nS:U - The mismanaged reference tracking, the WARN, and any resulting memory corruption all occur inside the kernel's own security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - The stale ax25_dev->dev_tracker pointer is dereferenced after the tracker object is recycled out of the 128-entry quarantine, giving a read of freed/reused slab memory whose contents the attacker can groom, which is an arbitrary-read style disclosure primitive; the WARN/ref_tracker splats additionally dump kernel addresses and stack traces.\nI:H - After the tracker is freed, ref_tracker_free() writes tracker->free_stack_handle and performs list_move_tail() on the reused object, yielding a list-unlink write with attacker-influenced pointers — memory corruption exploitable for control-flow hijacking.\nA:H - The bug reliably produces a WARNING at lib/ref_tracker.c:255 (a panic on panic_on_warn systems) plus a second WARN for leaked trackers at netdev teardown, and the freed-object path causes kernel oopses/heap corruption; the unreleased ax25_cb trackers also leak memory for the netdev's lifetime."
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