{ "schema_version": "1.6.1", "id": "RPI-CVE-2024-36968", "modified": "2026-10-09T11:39:44Z", "upstream": [ "CVE-2024-36968" ], "published": "2024-06-08T12:53:10Z", "summary": "Bluetooth: L2CAP: Fix div-by-zero in l2cap_le_flowctl_init()", "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nBluetooth: L2CAP: Fix div-by-zero in l2cap_le_flowctl_init()\n\nl2cap_le_flowctl_init() can cause both div-by-zero and an integer\noverflow since hdev->le_mtu may not fall in the valid range.\n\nMove MTU from hci_dev to hci_conn to validate MTU and stop the connection\nprocess earlier if MTU is invalid.\nAlso, add a missing validation in read_buffer_size() and make it return\nan error value if the validation fails.\nNow hci_conn_add() returns ERR_PTR() as it can fail due to the both a\nkzalloc failure and invalid MTU value.\n\ndivide error: 0000 [#1] PREEMPT SMP KASAN NOPTI\nCPU: 0 PID: 67 Comm: kworker/u5:0 Tainted: G W 6.9.0-rc5+ #20\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014\nWorkqueue: hci0 hci_rx_work\nRIP: 0010:l2cap_le_flowctl_init+0x19e/0x3f0 net/bluetooth/l2cap_core.c:547\nCode: e8 17 17 0c 00 66 41 89 9f 84 00 00 00 bf 01 00 00 00 41 b8 02 00 00 00 4c\n89 fe 4c 89 e2 89 d9 e8 27 17 0c 00 44 89 f0 31 d2 <66> f7 f3 89 c3 ff c3 4d 8d\nb7 88 00 00 00 4c 89 f0 48 c1 e8 03 42\nRSP: 0018:ffff88810bc0f858 EFLAGS: 00010246\nRAX: 00000000000002a0 RBX: 0000000000000000 RCX: dffffc0000000000\nRDX: 0000000000000000 RSI: ffff88810bc0f7c0 RDI: ffffc90002dcb66f\nRBP: ffff88810bc0f880 R08: aa69db2dda70ff01 R09: 0000ffaaaaaaaaaa\nR10: 0084000000ffaaaa R11: 0000000000000000 R12: ffff88810d65a084\nR13: dffffc0000000000 R14: 00000000000002a0 R15: ffff88810d65a000\nFS: 0000000000000000(0000) GS:ffff88811ac00000(0000) knlGS:0000000000000000\nCS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033\nCR2: 0000000020000100 CR3: 0000000103268003 CR4: 0000000000770ef0\nPKRU: 55555554\nCall Trace:\n \n l2cap_le_connect_req net/bluetooth/l2cap_core.c:4902 [inline]\n l2cap_le_sig_cmd net/bluetooth/l2cap_core.c:5420 [inline]\n l2cap_le_sig_channel net/bluetooth/l2cap_core.c:5486 [inline]\n l2cap_recv_frame+0xe59d/0x11710 net/bluetooth/l2cap_core.c:6809\n l2cap_recv_acldata+0x544/0x10a0 net/bluetooth/l2cap_core.c:7506\n hci_acldata_packet net/bluetooth/hci_core.c:3939 [inline]\n hci_rx_work+0x5e5/0xb20 net/bluetooth/hci_core.c:4176\n process_one_work kernel/workqueue.c:3254 [inline]\n process_scheduled_works+0x90f/0x1530 kernel/workqueue.c:3335\n worker_thread+0x926/0xe70 kernel/workqueue.c:3416\n kthread+0x2e3/0x380 kernel/kthread.c:388\n ret_from_fork+0x5c/0x90 arch/x86/kernel/process.c:147\n ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244\n \nModules linked in:\n---[ end trace 0000000000000000 ]---", "severity": [ { "type": "CVSS_V3", "score": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H" } ], "affected": [ { "package": { "ecosystem": "Raspberry Pi OS:12", "name": "linux" }, "versions": [ 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"6.6.20", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.6.32" }, "1:6.6.28-1+rpt1": { "linux_commit": "0c341f47adc3578cd5f817aa20ee2b7f9ae6b23e", "upstream_version": "6.6.28", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.6.32" }, "1:6.6.31-1+rpt1": { "linux_commit": "c1432b4bae5b6582f4d32ba381459f33c34d1424", "upstream_version": "6.6.31", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.6.32" } } } } ], "references": [ { "type": "ADVISORY", "url": "https://www.cve.org/CVERecord?id=CVE-2024-36968" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/ad3f7986c5a0f82b8b66a0afe1cc1f5421e1d674" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/dfece2b4e3759759b2bdfac2cd6d0ee9fbf055f3" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/d2b2f7d3936dc5990549bc36ab7ac7ac37f22c30" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/4d3dbaa252257d20611c3647290e6171f1bbd6c8" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/a5b862c6a221459d54e494e88965b48dcfa6cc44" } ], "database_specific": { "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git", "upstream_modified": "2026-08-05T11:52:36Z", "severity": { "source": "kernel CNA", "cvss_v3_score": 7.6, "cvss_v3_severity": "High", "scenario": "AV:A - The crash executes in `hci_rx_work` on receipt of an L2CAP LE Credit Based Connection Request from a Bluetooth LE peer in radio range, and the malformed buffer-size value originates from the HCI controller/transport \u2014 both are adjacent-network (Bluetooth PAN) attack surfaces, not routable network or purely local ones.\nAC:L - Nothing is probabilistic or beyond attacker control: an attacker owning the HCI transport (rogue USB/UART dongle or over-the-air-compromised controller firmware) sets `le_mtu` deterministically, and on a device whose controller reports an out-of-spec LE buffer size a single unauthenticated L2CAP packet triggers it on the first try.\nPR:N - `l2cap_le_connect_req()` is handled on the LE signalling channel and `smp_sufficient_security()` returns true immediately for the default `BT_SECURITY_LOW`, so no pairing, bonding, encryption or any local account is required.\nUI:N - The divide error occurs entirely inside the kernel receive workqueue when the L2CAP connect request is processed; no victim action such as accepting a pairing prompt or opening a file is involved.\nS:U - The faulting code and its impact are both inside the kernel's own security authority \u2014 no VM, IOMMU, or sandbox boundary is crossed.\nC:L - The unvalidated MTU underflows size computations in `l2cap_create_basic_pdu()` (`conn->mtu - L2CAP_HDR_SIZE`) and `l2cap_segment_sdu()` (size_t `pdu_len`) and inflates `chan->mps` past the real link MTU, giving bounded length confusion in L2CAP PDU construction plus register/state exposure in the oops, rather than an arbitrary read primitive.\nI:L - The same u16/size_t underflows let malformed, oversized L2CAP PDUs and credit values be built and transmitted with sizes partly steered by the peer's `remote_mps`, corrupting protocol state in a limited way short of an arbitrary kernel write.\nA:H - The `mps == 0` case is a hard divide error oops in the `hci_rx_work` kernel workqueue (fatal panic with panic_on_oops, dead Bluetooth stack otherwise), and the related `iso_mtu == 0` path spins forever in `iso_sock_sendmsg()` allocating skbs \u2014 an unrecoverable hang." } } }