{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2023-53827",
  "modified": "2026-10-09T11:39:44Z",
  "upstream": [
    "CVE-2023-53827"
  ],
  "published": "2025-12-09T01:31:24Z",
  "summary": "Bluetooth: L2CAP: Fix use-after-free in l2cap_disconnect_{req,rsp}",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nBluetooth: L2CAP: Fix use-after-free in l2cap_disconnect_{req,rsp}\n\nSimilar to commit d0be8347c623 (\"Bluetooth: L2CAP: Fix use-after-free\ncaused by l2cap_chan_put\"), just use l2cap_chan_hold_unless_zero to\nprevent referencing a channel that is about to be destroyed.",
  "severity": [
    {
      "type": "CVSS_V3",
      "score": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
    }
  ],
  "affected": [
    {
      "package": {
        "ecosystem": "Raspberry Pi OS:12",
        "name": "linux"
      },
      "versions": [
        "1:6.1.21-1+rpt1"
      ],
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "linux-image-6.1.0-rpi1-rpi-v6",
            "binary_version": "1:6.1.21-1+rpt1"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi1-rpi-v7",
            "binary_version": "1:6.1.21-1+rpt1"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi1-rpi-v7l",
            "binary_version": "1:6.1.21-1+rpt1"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi1-rpi-v8",
            "binary_version": "1:6.1.21-1+rpt1"
          }
        ]
      },
      "database_specific": {
        "per_version": {
          "1:6.1.21-1+rpt1": {
            "linux_commit": "0afb5e98488aed7017b9bf321b575d0177feb7ed",
            "upstream_version": "6.1.21",
            "assessment": "commit ancestry (strak rule)",
            "upstream_fixed": "6.1.25"
          }
        }
      }
    }
  ],
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2023-53827"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/f2d38e77aa5f3effc143e7dd24da8acf02925958"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/1351551aa9058e07a20a27a158270cf84fcde621"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/c02421992505c95c7f3c9ad59ee35e22eac60988"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/d9ba36c22a7bb09d6bac4cc2f243eff05da53f43"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/ac6725a634f7e8c0330610a8527f20c730b61115"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/348d446762e7c70778df8bafbdf3fa0df2123f58"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/d82a439c3cfdb28aa7e82e2e849c5c4dd9fca284"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/a2a9339e1c9deb7e1e079e12e27a0265aea8421a"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-08-05T11:24:39Z",
    "severity": {
      "source": "kernel CNA",
      "cvss_v3_score": 8.8,
      "cvss_v3_severity": "High",
      "scenario": "AV:A - The vulnerable code is reached only by processing an L2CAP Disconnect Request/Response signalling PDU received from a Bluetooth peer over a BR/EDR ACL or LE link, which requires the attacker to be within Bluetooth radio range. Per kernel scoring guidance, Bluetooth-reachable code is Adjacent.\nAC:L - The attacker drives both sides: it creates and tears down L2CAP channels at will (CONN_REQ/DISCONN_REQ, ECRED reconfigure responses that call l2cap_chan_del with no lock) while flooding disconnect signalling to hit the window where the kref has reached zero but the channel is still on conn->chan_l, and can retry the connect/disconnect cycle indefinitely at no cost. syzbot reproduced the identical pattern in the sibling handler.\nPR:N - l2cap_recv_frame dispatches CID 0x0001/0x0005 straight to the signalling handlers with no security-level, pairing, or encryption check, so an entirely unauthenticated, unpaired in-range device can send the triggering PDU. Fixed channels present on conn->chan_l give a valid target CID without any local socket.\nUI:N - No victim action is needed \u2014 the packet is processed by hci_rx_work as soon as it arrives on a connectable/advertising host with Bluetooth enabled, which is the default on phones, cars, headsets and laptops.\nS:U - The corruption and its consequences are confined to the kernel's own security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - The handler reads chan->scid and chan->dcid out of the freed kmalloc-1k object and echoes them to the attacker in the Disconnect Response, giving a repeatable remote leak of reclaimed kernel heap contents, and the broader use-after-free permits arbitrary read via heap grooming.\nI:H - After the increment-on-zero the code performs three indirect calls (chan->ops->set_shutdown, ->teardown, ->close) through function pointers read from the freed object plus a list_del on freed list heads, so an attacker who sprays the reclaimed kmalloc-1024 slot obtains control-flow hijack and arbitrary-write primitives.\nA:H - The bug is a KASAN-confirmed use-after-free that mutex_locks freed memory and triggers a refcount_t \"increment on 0\" splat, reliably producing a kernel oops/panic, and it can be re-triggered remotely at will."
    }
  }
}