fkie_cve-2025-39985
Vulnerability from fkie_nvd
Published
2025-10-15 08:15
Modified
2025-10-16 15:29
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: can: mcba_usb: populate ndo_change_mtu() to prevent buffer overflow Sending an PF_PACKET allows to bypass the CAN framework logic and to directly reach the xmit() function of a CAN driver. The only check which is performed by the PF_PACKET framework is to make sure that skb->len fits the interface's MTU. Unfortunately, because the mcba_usb driver does not populate its net_device_ops->ndo_change_mtu(), it is possible for an attacker to configure an invalid MTU by doing, for example: $ ip link set can0 mtu 9999 After doing so, the attacker could open a PF_PACKET socket using the ETH_P_CANXL protocol: socket(PF_PACKET, SOCK_RAW, htons(ETH_P_CANXL)) to inject a malicious CAN XL frames. For example: struct canxl_frame frame = { .flags = 0xff, .len = 2048, }; The CAN drivers' xmit() function are calling can_dev_dropped_skb() to check that the skb is valid, unfortunately under above conditions, the malicious packet is able to go through can_dev_dropped_skb() checks: 1. the skb->protocol is set to ETH_P_CANXL which is valid (the function does not check the actual device capabilities). 2. the length is a valid CAN XL length. And so, mcba_usb_start_xmit() receives a CAN XL frame which it is not able to correctly handle and will thus misinterpret it as a CAN frame. This can result in a buffer overflow. The driver will consume cf->len as-is with no further checks on these lines: usb_msg.dlc = cf->len; memcpy(usb_msg.data, cf->data, usb_msg.dlc); Here, cf->len corresponds to the flags field of the CAN XL frame. In our previous example, we set canxl_frame->flags to 0xff. Because the maximum expected length is 8, a buffer overflow of 247 bytes occurs! Populate net_device_ops->ndo_change_mtu() to ensure that the interface's MTU can not be set to anything bigger than CAN_MTU. By fixing the root cause, this prevents the buffer overflow.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/0fa9303c4b9493727e0d3a6ac3729300e3013930
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/17c8d794527f01def0d1c8b7dc2d7b8d34fed0e6
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/3664ae91b26d1fd7e4cee9cde17301361f4c89d5
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/37aed407496bf6de8910e588edb04d2435fa7011
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/6b9fb82df8868dbe9ffea5874b8d35f951faedbb
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/6eec67bfb25637f9b51e584cf59ddace59925bc8
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/b638c3fb0f163e69785ceddb3b434a9437878bec
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/ca4e51359608e1f29bf1f2c33c3ddf775b6b7ed1
Impacted products
Vendor Product Version


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{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "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-\u003elen fits the interface\u0027s MTU.\n\nUnfortunately, because the mcba_usb driver does not populate its\nnet_device_ops-\u003endo_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\u0027 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-\u003eprotocol 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-\u003elen\nas-is with no further checks on these lines:\n\n\tusb_msg.dlc = cf-\u003elen;\n\n\tmemcpy(usb_msg.data, cf-\u003edata, usb_msg.dlc);\n\nHere, cf-\u003elen corresponds to the flags field of the CAN XL frame. In\nour previous example, we set canxl_frame-\u003eflags to 0xff. Because the\nmaximum expected length is 8, a buffer overflow of 247 bytes occurs!\n\nPopulate net_device_ops-\u003endo_change_mtu() to ensure that the\ninterface\u0027s MTU can not be set to anything bigger than CAN_MTU. By\nfixing the root cause, this prevents the buffer overflow."
    }
  ],
  "id": "CVE-2025-39985",
  "lastModified": "2025-10-16T15:29:11.563",
  "metrics": {},
  "published": "2025-10-15T08:15:36.523",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/0fa9303c4b9493727e0d3a6ac3729300e3013930"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/17c8d794527f01def0d1c8b7dc2d7b8d34fed0e6"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/3664ae91b26d1fd7e4cee9cde17301361f4c89d5"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/37aed407496bf6de8910e588edb04d2435fa7011"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/6b9fb82df8868dbe9ffea5874b8d35f951faedbb"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/6eec67bfb25637f9b51e584cf59ddace59925bc8"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/b638c3fb0f163e69785ceddb3b434a9437878bec"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/ca4e51359608e1f29bf1f2c33c3ddf775b6b7ed1"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Awaiting Analysis"
}


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