CVE-2026-46275 (GCVE-0-2026-46275)
Vulnerability from cvelistv5
Published
2026-06-08 14:30
Modified
2026-08-05 12:30
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: Bluetooth: hci_uart: fix UAFs and race conditions in close and init paths Vulnerabilities leading to Use-After-Free (UAF) and Null Pointer Dereference (NPD) conditions were observed in the lifecycle management of hci_uart. The primary issue arises because the workqueues (init_ready and write_work) are only flushed/cancelled if the HCI_UART_PROTO_READY flag is set during TTY close. If a hangup occurs before setup completes, hci_uart_tty_close() skips the teardown of these workqueues and proceeds to free the `hu` struct. When the scheduled work executes later, it blindly dereferences the freed `hu` struct. Furthermore, several data races and UAFs were identified in the teardown sequence: 1. Calling hci_uart_flush() from hci_uart_close() without effectively disabling write_work causes a race condition where both can concurrently double-free hu->tx_skb. This happens because protocol timers can concurrently invoke hci_uart_tx_wakeup() and requeue write_work. 2. Calling hci_free_dev(hdev) before hu->proto->close(hu) causes a UAF when vendor specific protocol close callbacks dereference hu->hdev. 3. In the initialization error paths, failing to take the proto_lock write lock before clearing PROTO_READY leads to races with active readers. Additionally, hci_uart_tty_receive() accesses hu->hdev outside the read lock, leading to UAFs if the initialization error path frees hdev concurrently. Fix these synchronization and lifecycle issues by: 1. Re-ordering hci_uart_tty_close() to clear HCI_UART_PROTO_READY first, followed immediately by a cancel_work_sync(&hu->write_work). Clearing the flag locks out concurrent protocol timers from successfully invoking hci_uart_tx_wakeup(), effectively rendering the cancellation permanent and preventing the tx_skb double-free. 2. Note: Clearing PROTO_READY early causes hci_uart_close() to skip hu->proto->flush(). This is perfectly safe in the tty_close path because hu->proto->close() executes shortly after, which intrinsically purges all protocol SKB queues and tears down the state. 3. Relocating hu->proto->close(hu) strictly prior to hci_free_dev(hdev) across all close and error paths to prevent vendor-level UAFs. 4. Moving the hdev->stat.byte_rx increment in hci_uart_tty_receive() inside the proto_lock read-side critical section to safely synchronize with device unregistration. 5. Adding cancel_work_sync(&hu->write_work) to hci_uart_close() to safely flush the workqueue before hci_uart_flush() is invoked via the HCI core. 6. Utilizing cancel_work_sync() instead of disable_work_sync() across all paths to prevent permanently breaking user-space retry capabilities.
References
Impacted products
Vendor Product Version
Linux Linux Version: 3b799254cf6f481460719023d7a18f46651e5e7f
Version: 3b799254cf6f481460719023d7a18f46651e5e7f
Version: 3b799254cf6f481460719023d7a18f46651e5e7f
Version: 3b799254cf6f481460719023d7a18f46651e5e7f
Version: 3b799254cf6f481460719023d7a18f46651e5e7f
Version: 3b799254cf6f481460719023d7a18f46651e5e7f
Version: 3b799254cf6f481460719023d7a18f46651e5e7f
Version: 3b799254cf6f481460719023d7a18f46651e5e7f
Version: cd27019bc149f20f12ebec943c2b4c775745a5a0
Version: aea63181b6fcb6b9ccde1ada9ea51be19c4015af
Version: 0d234d1135dcd8876de0576dac68efd0a87eef87
Version: 3fe978892ab46efc2f3830d9abc015eff72caaf9
Version: 0d987e14bebaf0f67ee7dbefaf6165c62cd1d27f
Version: 4.14.203   ≤
Version: 4.19.153   ≤
Version: 5.4.73   ≤
Version: 5.8.17   ≤
Version: 5.9.2   ≤
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nBluetooth: hci_uart: fix UAFs and race conditions in close and init paths\n\nVulnerabilities leading to Use-After-Free (UAF) and Null Pointer\nDereference (NPD) conditions were observed in the lifecycle management\nof hci_uart.\n\nThe primary issue arises because the workqueues (init_ready and\nwrite_work) are only flushed/cancelled if the HCI_UART_PROTO_READY\nflag is set during TTY close. If a hangup occurs before setup completes,\nhci_uart_tty_close() skips the teardown of these workqueues and\nproceeds to free the `hu` struct. When the scheduled work executes\nlater, it blindly dereferences the freed `hu` struct.\n\nFurthermore, several data races and UAFs were identified in the teardown\nsequence:\n1. Calling hci_uart_flush() from hci_uart_close() without effectively\n   disabling write_work causes a race condition where both can concurrently\n   double-free hu-\u003etx_skb. This happens because protocol timers can\n   concurrently invoke hci_uart_tx_wakeup() and requeue write_work.\n2. Calling hci_free_dev(hdev) before hu-\u003eproto-\u003eclose(hu) causes a UAF\n   when vendor specific protocol close callbacks dereference hu-\u003ehdev.\n3. In the initialization error paths, failing to take the proto_lock\n   write lock before clearing PROTO_READY leads to races with active\n   readers. Additionally, hci_uart_tty_receive() accesses hu-\u003ehdev\n   outside the read lock, leading to UAFs if the initialization error\n   path frees hdev concurrently.\n\nFix these synchronization and lifecycle issues by:\n1. Re-ordering hci_uart_tty_close() to clear HCI_UART_PROTO_READY first,\n   followed immediately by a cancel_work_sync(\u0026hu-\u003ewrite_work). Clearing\n   the flag locks out concurrent protocol timers from successfully invoking\n   hci_uart_tx_wakeup(), effectively rendering the cancellation permanent\n   and preventing the tx_skb double-free.\n2. Note: Clearing PROTO_READY early causes hci_uart_close() to skip\n   hu-\u003eproto-\u003eflush(). This is perfectly safe in the tty_close path\n   because hu-\u003eproto-\u003eclose() executes shortly after, which intrinsically\n   purges all protocol SKB queues and tears down the state.\n3. Relocating hu-\u003eproto-\u003eclose(hu) strictly prior to hci_free_dev(hdev)\n   across all close and error paths to prevent vendor-level UAFs.\n4. Moving the hdev-\u003estat.byte_rx increment in hci_uart_tty_receive()\n   inside the proto_lock read-side critical section to safely synchronize\n   with device unregistration.\n5. Adding cancel_work_sync(\u0026hu-\u003ewrite_work) to hci_uart_close() to safely\n   flush the workqueue before hci_uart_flush() is invoked via the HCI core.\n6. Utilizing cancel_work_sync() instead of disable_work_sync() across\n   all paths to prevent permanently breaking user-space retry capabilities."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - Exploitation requires local TTY control (TIOCSETD to N_HCI, HCIUARTSETPROTO ioctl, hangup/close) gated by CAP_NET_ADMIN at hci_uart_tty_open(); the bugs are in driver lifecycle teardown, not in processing of remote Bluetooth over-the-air packets.\nAC:L - The attacker controls both sides of every race by concurrently opening/closing the TTY line discipline, issuing HCIUART ioctls, and timing hangup against in-flight workqueues and protocol timers; UAF conditions are reliably winnable without luck-dependent memory layout.\nPR:L - hci_uart_tty_open() explicitly requires CAP_NET_ADMIN, and adapter teardown paths are similarly admin-gated; CAP_NET_ADMIN is obtainable by an unprivileged user inside a user namespace, satisfying the Low privileges threshold rather than High.\nUI:N - Once the attacker has the required local TTY/HCI access, triggering the UAF or double-free races requires no action from a separate victim user.\nS:U - The vulnerability corrupts kernel heap memory within the kernel\u0027s own security boundary; successful exploitation yields kernel privilege escalation, not a cross-boundary escape such as VM or sandbox breakout.\nC:H - Multiple use-after-free conditions on the hci_uart and hci_dev structures allow dereferencing attacker-influenced freed memory, providing a standard kernel info-leak primitive consistent with UAF severity guidance.\nI:H - The UAF and hu-\u003etx_skb double-free races enable control of freed slab objects and heap grooming, providing a path to arbitrary kernel memory corruption and potential code execution in kernel context.\nA:H - Use-after-free and double-free in kernel workqueue and teardown paths reliably cause kernel oops or panic, and can be triggered repeatedly to deny availability of the affected system."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:30:58.918Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/78aad93e938f013d9272fe0ee168f27883afa95c"
        },
        {
          "url": "https://git.kernel.org/stable/c/e2d19969c8d9198ecc3090bcd5312ecd503a3339"
        },
        {
          "url": "https://git.kernel.org/stable/c/c85cff648a2bc92322912db5f1727ad05afae7b6"
        },
        {
          "url": "https://git.kernel.org/stable/c/9d20d48be2c4a071fb015eb09bda2cecd25daf34"
        },
        {
          "url": "https://git.kernel.org/stable/c/81c7a3c22a0f2808cf4ae0b4908f59763b23606d"
        },
        {
          "url": "https://git.kernel.org/stable/c/192cb0f1ca706d9a1bc36ae0ad5f666d1e4fd894"
        },
        {
          "url": "https://git.kernel.org/stable/c/7338031946bd06f6dff149e67b60c4cd083bfea8"
        },
        {
          "url": "https://git.kernel.org/stable/c/c1bb9336ae6b54a5f6a353c4bd4ed9a4307e429b"
        }
      ],
      "title": "Bluetooth: hci_uart: fix UAFs and race conditions in close and init paths",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-46275",
    "datePublished": "2026-06-08T14:30:54.232Z",
    "dateReserved": "2026-05-13T15:03:33.109Z",
    "dateUpdated": "2026-08-05T12:30:58.918Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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