GHSA-C684-Q9WG-VHH9

Vulnerability from github – Published: 2025-09-22 21:30 – Updated: 2026-05-12 15:31
VLAI
Details

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

Bluetooth: Fix use-after-free in l2cap_sock_cleanup_listen()

syzbot reported the splat below without a repro.

In the splat, a single thread calling bt_accept_dequeue() freed sk and touched it after that.

The root cause would be the racy l2cap_sock_cleanup_listen() call added by the cited commit.

bt_accept_dequeue() is called under lock_sock() except for l2cap_sock_release().

Two threads could see the same socket during the list iteration in bt_accept_dequeue():

CPU1 CPU2 (close()) ---- ---- sock_hold(sk) sock_hold(sk); lock_sock(sk) <-- block close() sock_put(sk) bt_accept_unlink(sk) sock_put(sk) <-- refcnt by bt_accept_enqueue() release_sock(sk) lock_sock(sk) sock_put(sk) bt_accept_unlink(sk) sock_put(sk) <-- last refcnt bt_accept_unlink(sk) <-- UAF

Depending on the timing, the other thread could show up in the "Freed by task" part.

Let's call l2cap_sock_cleanup_listen() under lock_sock() in l2cap_sock_release().

[0]: BUG: KASAN: slab-use-after-free in debug_spin_lock_before kernel/locking/spinlock_debug.c:86 [inline] BUG: KASAN: slab-use-after-free in do_raw_spin_lock+0x26f/0x2b0 kernel/locking/spinlock_debug.c:115 Read of size 4 at addr ffff88803b7eb1c4 by task syz.5.3276/16995 CPU: 3 UID: 0 PID: 16995 Comm: syz.5.3276 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0xcd/0x630 mm/kasan/report.c:482 kasan_report+0xe0/0x110 mm/kasan/report.c:595 debug_spin_lock_before kernel/locking/spinlock_debug.c:86 [inline] do_raw_spin_lock+0x26f/0x2b0 kernel/locking/spinlock_debug.c:115 spin_lock_bh include/linux/spinlock.h:356 [inline] release_sock+0x21/0x220 net/core/sock.c:3746 bt_accept_dequeue+0x505/0x600 net/bluetooth/af_bluetooth.c:312 l2cap_sock_cleanup_listen+0x5c/0x2a0 net/bluetooth/l2cap_sock.c:1451 l2cap_sock_release+0x5c/0x210 net/bluetooth/l2cap_sock.c:1425 __sock_release+0xb3/0x270 net/socket.c:649 sock_close+0x1c/0x30 net/socket.c:1439 __fput+0x3ff/0xb70 fs/file_table.c:468 task_work_run+0x14d/0x240 kernel/task_work.c:227 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] exit_to_user_mode_loop+0xeb/0x110 kernel/entry/common.c:43 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline] syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline] syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline] do_syscall_64+0x3f6/0x4c0 arch/x86/entry/syscall_64.c:100 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f2accf8ebe9 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffdb6cb1378 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4 RAX: 0000000000000000 RBX: 00000000000426fb RCX: 00007f2accf8ebe9 RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003 RBP: 00007f2acd1b7da0 R08: 0000000000000001 R09: 00000012b6cb166f R10: 0000001b30e20000 R11: 0000000000000246 R12: 00007f2acd1b609c R13: 00007f2acd1b6090 R14: ffffffffffffffff R15: 00007ffdb6cb1490

Allocated by task 5326: kasan_save_stack+0x33/0x60 mm/kasan/common.c:47 kasan_save_track+0x14/0x30 mm/kasan/common.c:68 poison_kmalloc_redzone mm/kasan/common.c:388 [inline] __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:405 kasan_kmalloc include/linux/kasan.h:260 [inline] __do_kmalloc_node mm/slub.c:4365 [inline] __kmalloc_nopro ---truncated---

Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Show details on source website
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{
  "affected": [],
  "aliases": [
    "CVE-2025-39860"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-416"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-09-19T16:15:44Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nBluetooth: Fix use-after-free in l2cap_sock_cleanup_listen()\n\nsyzbot reported the splat below without a repro.\n\nIn the splat, a single thread calling bt_accept_dequeue() freed sk\nand touched it after that.\n\nThe root cause would be the racy l2cap_sock_cleanup_listen() call\nadded by the cited commit.\n\nbt_accept_dequeue() is called under lock_sock() except for\nl2cap_sock_release().\n\nTwo threads could see the same socket during the list iteration\nin bt_accept_dequeue():\n\n  CPU1                        CPU2 (close())\n  ----                        ----\n  sock_hold(sk)               sock_hold(sk);\n  lock_sock(sk)   \u003c-- block close()\n  sock_put(sk)\n  bt_accept_unlink(sk)\n    sock_put(sk)  \u003c-- refcnt by bt_accept_enqueue()\n  release_sock(sk)\n                              lock_sock(sk)\n                              sock_put(sk)\n                              bt_accept_unlink(sk)\n                                sock_put(sk)        \u003c-- last refcnt\n                              bt_accept_unlink(sk)  \u003c-- UAF\n\nDepending on the timing, the other thread could show up in the\n\"Freed by task\" part.\n\nLet\u0027s call l2cap_sock_cleanup_listen() under lock_sock() in\nl2cap_sock_release().\n\n[0]:\nBUG: KASAN: slab-use-after-free in debug_spin_lock_before kernel/locking/spinlock_debug.c:86 [inline]\nBUG: KASAN: slab-use-after-free in do_raw_spin_lock+0x26f/0x2b0 kernel/locking/spinlock_debug.c:115\nRead of size 4 at addr ffff88803b7eb1c4 by task syz.5.3276/16995\nCPU: 3 UID: 0 PID: 16995 Comm: syz.5.3276 Not tainted syzkaller #0 PREEMPT(full)\nHardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014\nCall Trace:\n \u003cTASK\u003e\n __dump_stack lib/dump_stack.c:94 [inline]\n dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120\n print_address_description mm/kasan/report.c:378 [inline]\n print_report+0xcd/0x630 mm/kasan/report.c:482\n kasan_report+0xe0/0x110 mm/kasan/report.c:595\n debug_spin_lock_before kernel/locking/spinlock_debug.c:86 [inline]\n do_raw_spin_lock+0x26f/0x2b0 kernel/locking/spinlock_debug.c:115\n spin_lock_bh include/linux/spinlock.h:356 [inline]\n release_sock+0x21/0x220 net/core/sock.c:3746\n bt_accept_dequeue+0x505/0x600 net/bluetooth/af_bluetooth.c:312\n l2cap_sock_cleanup_listen+0x5c/0x2a0 net/bluetooth/l2cap_sock.c:1451\n l2cap_sock_release+0x5c/0x210 net/bluetooth/l2cap_sock.c:1425\n __sock_release+0xb3/0x270 net/socket.c:649\n sock_close+0x1c/0x30 net/socket.c:1439\n __fput+0x3ff/0xb70 fs/file_table.c:468\n task_work_run+0x14d/0x240 kernel/task_work.c:227\n resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]\n exit_to_user_mode_loop+0xeb/0x110 kernel/entry/common.c:43\n exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]\n syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]\n syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]\n do_syscall_64+0x3f6/0x4c0 arch/x86/entry/syscall_64.c:100\n entry_SYSCALL_64_after_hwframe+0x77/0x7f\nRIP: 0033:0x7f2accf8ebe9\nCode: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 \u003c48\u003e 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48\nRSP: 002b:00007ffdb6cb1378 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4\nRAX: 0000000000000000 RBX: 00000000000426fb RCX: 00007f2accf8ebe9\nRDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003\nRBP: 00007f2acd1b7da0 R08: 0000000000000001 R09: 00000012b6cb166f\nR10: 0000001b30e20000 R11: 0000000000000246 R12: 00007f2acd1b609c\nR13: 00007f2acd1b6090 R14: ffffffffffffffff R15: 00007ffdb6cb1490\n \u003c/TASK\u003e\n\nAllocated by task 5326:\n kasan_save_stack+0x33/0x60 mm/kasan/common.c:47\n kasan_save_track+0x14/0x30 mm/kasan/common.c:68\n poison_kmalloc_redzone mm/kasan/common.c:388 [inline]\n __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:405\n kasan_kmalloc include/linux/kasan.h:260 [inline]\n __do_kmalloc_node mm/slub.c:4365 [inline]\n __kmalloc_nopro\n---truncated---",
  "id": "GHSA-c684-q9wg-vhh9",
  "modified": "2026-05-12T15:31:10Z",
  "published": "2025-09-22T21:30:18Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-39860"
    },
    {
      "type": "WEB",
      "url": "https://cert-portal.siemens.com/productcert/html/ssa-032379.html"
    },
    {
      "type": "WEB",
      "url": "https://cert-portal.siemens.com/productcert/html/ssa-089022.html"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2ca99fc3512a8074de20ee52a87b492dfcc41a4d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/306b0991413b482dbf5585b423022123bb505966"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3dff390f55ccd9ce12e91233849769b5312180c2"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/47f6090bcf75c369695d21c3f179db8a56bbbd49"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6077d16b5c0f65d571eee709de2f0541fb5ef0ca"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/83e1d9892ef51785cf0760b7681436760dda435a"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/862c628108562d8c7a516a900034823b381d3cba"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/964cbb198f9c46c2b2358cd1faffc04c1e8248cf"
    },
    {
      "type": "WEB",
      "url": "https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html"
    },
    {
      "type": "WEB",
      "url": "https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}



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