{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2025-39985",
  "modified": "2026-10-07T17:22:01Z",
  "upstream": [
    "CVE-2025-39985"
  ],
  "published": "2025-10-15T07:57:23Z",
  "summary": "can: mcba_usb: populate ndo_change_mtu() to prevent buffer overflow",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\ncan: mcba_usb: populate ndo_change_mtu() to prevent buffer overflow\n\nSending an PF_PACKET allows to bypass the CAN framework logic and to\ndirectly reach the xmit() function of a CAN driver. The only check\nwhich is performed by the PF_PACKET framework is to make sure that\nskb->len fits the interface's MTU.\n\nUnfortunately, because the mcba_usb driver does not populate its\nnet_device_ops->ndo_change_mtu(), it is possible for an attacker to\nconfigure an invalid MTU by doing, for example:\n\n  $ ip link set can0 mtu 9999\n\nAfter doing so, the attacker could open a PF_PACKET socket using the\nETH_P_CANXL protocol:\n\n\tsocket(PF_PACKET, SOCK_RAW, htons(ETH_P_CANXL))\n\nto inject a malicious CAN XL frames. For example:\n\n\tstruct canxl_frame frame = {\n\t\t.flags = 0xff,\n\t\t.len = 2048,\n\t};\n\nThe CAN drivers' xmit() function are calling can_dev_dropped_skb() to\ncheck that the skb is valid, unfortunately under above conditions, the\nmalicious packet is able to go through can_dev_dropped_skb() checks:\n\n  1. the skb->protocol is set to ETH_P_CANXL which is valid (the\n     function does not check the actual device capabilities).\n\n  2. the length is a valid CAN XL length.\n\nAnd so, mcba_usb_start_xmit() receives a CAN XL frame which it is not\nable to correctly handle and will thus misinterpret it as a CAN frame.\n\nThis can result in a buffer overflow. The driver will consume cf->len\nas-is with no further checks on these lines:\n\n\tusb_msg.dlc = cf->len;\n\n\tmemcpy(usb_msg.data, cf->data, usb_msg.dlc);\n\nHere, cf->len corresponds to the flags field of the CAN XL frame. In\nour previous example, we set canxl_frame->flags to 0xff. Because the\nmaximum expected length is 8, a buffer overflow of 247 bytes occurs!\n\nPopulate net_device_ops->ndo_change_mtu() to ensure that the\ninterface's MTU can not be set to anything bigger than CAN_MTU. By\nfixing the root cause, this prevents the buffer overflow.",
  "affected": [
    {
      "package": {
        "ecosystem": "Raspberry Pi OS:12",
        "name": "linux"
      },
      "versions": [
        "1:6.1.47-1+rpt4"
      ],
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-2712",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v6",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7l",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v8",
            "binary_version": "1:6.1.47-1+rpt4"
          }
        ]
      },
      "database_specific": {
        "per_version": {
          "1:6.1.47-1+rpt4": {
            "linux_commit": "655fc658a15ae7a6f37103754adb39ba52a9a14e",
            "upstream_version": "6.1.47",
            "assessment": "commit ancestry (strak rule)",
            "upstream_fixed": "6.1.155",
            "compiled_filter": false
          }
        }
      }
    }
  ],
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2025-39985"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/0fa9303c4b9493727e0d3a6ac3729300e3013930"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/37aed407496bf6de8910e588edb04d2435fa7011"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/6eec67bfb25637f9b51e584cf59ddace59925bc8"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/ca4e51359608e1f29bf1f2c33c3ddf775b6b7ed1"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/3664ae91b26d1fd7e4cee9cde17301361f4c89d5"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/6b9fb82df8868dbe9ffea5874b8d35f951faedbb"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/b638c3fb0f163e69785ceddb3b434a9437878bec"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/17c8d794527f01def0d1c8b7dc2d7b8d34fed0e6"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-08-05T12:19:11Z"
  }
}