GHSA-XQVM-46MC-2MF2

Vulnerability from github – Published: 2026-09-11 21:31 – Updated: 2026-09-14 15:32
VLAI
Details

In the Linux kernel, the following vulnerability has been resolved:

ALSA: 6fire: bound the MIDI event length from the device

usb6fire_comm_receiver_handler() forwards a MIDI event using a length byte the device supplies, with no bound and no check that the transfer delivered that many bytes:

if (!urb->status) {
    if (rt->receiver_buffer[0] == 0x10) /* midi in event */
        if (midi_rt)
            midi_rt->in_received(midi_rt,
                    rt->receiver_buffer + 2,
                    rt->receiver_buffer[1]);
}

receiver_buffer is a 64-byte kzalloc() buffer (COMM_RECEIVER_BUFSIZE), so only 62 bytes follow the two-byte header. receiver_buffer[1] is a u8 the device chooses, so a device that answers with 0x10 and a length of 0xFF makes snd_rawmidi_receive() read 255 bytes starting two bytes into a 64-byte object. The bytes past the buffer are handed to userspace through the rawmidi read path.

urb->actual_length is not consulted either, so a short transfer leaves both the type byte and the length byte at their previous values and the handler acts on stale data.

The receiver URB is submitted from usb6fire_comm_init() at probe, so the read happens on plug with no user action; forwarding to userspace also needs a MIDI input substream open, since usb6fire_midi_in_received() only calls snd_rawmidi_receive() when rt->in is set.

KASAN on 7.2.0-rc5 (arm64), single packet from an emulated device:

BUG: KASAN: slab-out-of-bounds in snd_rawmidi_receive Read of size 255 at addr ffff000009f64682 by task bash/183 __asan_memcpy snd_rawmidi_receive usb6fire_midi_in_received [snd_usb_6fire] usb6fire_comm_receiver_handler [snd_usb_6fire] Allocated by task 11: usb6fire_comm_init [snd_usb_6fire] usb6fire_chip_probe [snd_usb_6fire] The buggy address is located 2 bytes inside of allocated 64-byte region [ffff000009f64680, ffff000009f646c0)

Reject the event when the length exceeds the bytes that follow the header, and require the transfer to have delivered the header plus that many bytes. The receiver URB is submitted with a 64-byte transfer_buffer_length, so a genuine device cannot deliver an event longer than those 62 bytes and nothing valid is dropped.

Discovered by XBOW, triaged by Baul Lee baul.lee@xbow.com

Show details on source website
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{
  "affected": [],
  "aliases": [
    "CVE-2026-80973"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-11T20:19:03Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: 6fire: bound the MIDI event length from the device\n\nusb6fire_comm_receiver_handler() forwards a MIDI event using a length\nbyte the device supplies, with no bound and no check that the transfer\ndelivered that many bytes:\n\n\tif (!urb-\u003estatus) {\n\t\tif (rt-\u003ereceiver_buffer[0] == 0x10) /* midi in event */\n\t\t\tif (midi_rt)\n\t\t\t\tmidi_rt-\u003ein_received(midi_rt,\n\t\t\t\t\t\trt-\u003ereceiver_buffer + 2,\n\t\t\t\t\t\trt-\u003ereceiver_buffer[1]);\n\t}\n\nreceiver_buffer is a 64-byte kzalloc() buffer (COMM_RECEIVER_BUFSIZE), so\nonly 62 bytes follow the two-byte header.  receiver_buffer[1] is a u8 the\ndevice chooses, so a device that answers with 0x10 and a length of 0xFF\nmakes snd_rawmidi_receive() read 255 bytes starting two bytes into a\n64-byte object.  The bytes past the buffer are handed to userspace\nthrough the rawmidi read path.\n\nurb-\u003eactual_length is not consulted either, so a short transfer leaves\nboth the type byte and the length byte at their previous values and the\nhandler acts on stale data.\n\nThe receiver URB is submitted from usb6fire_comm_init() at probe, so the\nread happens on plug with no user action; forwarding to userspace also\nneeds a MIDI input substream open, since usb6fire_midi_in_received()\nonly calls snd_rawmidi_receive() when rt-\u003ein is set.\n\nKASAN on 7.2.0-rc5 (arm64), single packet from an emulated device:\n\n  BUG: KASAN: slab-out-of-bounds in snd_rawmidi_receive\n  Read of size 255 at addr ffff000009f64682 by task bash/183\n   __asan_memcpy\n   snd_rawmidi_receive\n   usb6fire_midi_in_received [snd_usb_6fire]\n   usb6fire_comm_receiver_handler [snd_usb_6fire]\n  Allocated by task 11:\n   usb6fire_comm_init [snd_usb_6fire]\n   usb6fire_chip_probe [snd_usb_6fire]\n  The buggy address is located 2 bytes inside of\n   allocated 64-byte region [ffff000009f64680, ffff000009f646c0)\n\nReject the event when the length exceeds the bytes that follow the\nheader, and require the transfer to have delivered the header plus that\nmany bytes.  The receiver URB is submitted with a 64-byte\ntransfer_buffer_length, so a genuine device cannot deliver an event\nlonger than those 62 bytes and nothing valid is dropped.\n\nDiscovered by XBOW, triaged by Baul Lee \u003cbaul.lee@xbow.com\u003e",
  "id": "GHSA-xqvm-46mc-2mf2",
  "modified": "2026-09-14T15:32:21Z",
  "published": "2026-09-11T21:31:22Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-80973"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/00e84a9ff2d43953ae261995cae94d46f4c307a6"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0c8a3c773823cf12abd39c480aed70e25c384630"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2a6f6fba3bd31d2e8c957fefa29156e35e5e75d5"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2c590d5e1b1595d5c8fa0b72d2897423ce9985ca"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/34816e2cfeabafb8eccf54687186ce25699e8363"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/466e911bbbbb779bb06337e35a286e5ca7af16b3"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a478893b59e36cfe7d77a76b352f2db55502e879"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c9204bc2ed2010e2469dbe5fce598878a37efd04"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}



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