GHSA-27WQ-XJR3-W8C9
Vulnerability from github – Published: 2026-09-11 21:31 – Updated: 2026-09-14 15:32In the Linux kernel, the following vulnerability has been resolved:
ALSA: bcd2000: clear the URB pointers on disconnect
bcd2000_free_usb_related_resources() frees both URBs and leaves the pointers behind:
usb_kill_urb(bcd2k->midi_out_urb);
usb_kill_urb(bcd2k->midi_in_urb);
usb_free_urb(bcd2k->midi_out_urb);
usb_free_urb(bcd2k->midi_in_urb);
The rawmidi device outlives that call. A substream that is still open when the device is unplugged reaches bcd2000_midi_send() from the trigger path on close. That function writes to the freed URB and then hands it to the USB core:
bcd2k->midi_out_urb->transfer_buffer_length = BUFSIZE;
...
ret = usb_submit_urb(bcd2k->midi_out_urb, GFP_ATOMIC);
usb_kill_urb() does not stop a later submission either, so a submit that races the disconnect can requeue the URB after it has been reaped. midi_in_urb is exposed the same way: bcd2000_input_complete() resubmits it from the completion handler.
KASAN on 7.2.0-rc5 (arm64):
BUG: KASAN: slab-use-after-free in bcd2000_midi_send [snd_bcd2000] Write of size 4 at addr ffff00001827d388 by task bpoc/168 __asan_store4 bcd2000_midi_send [snd_bcd2000] bcd2000_midi_output_trigger [snd_bcd2000] snd_rawmidi_kernel_write1 close_substream.part.0 Freed by task 168: usb_free_urb bcd2000_disconnect [snd_bcd2000]
BUG: KASAN: slab-use-after-free in usb_submit_urb Read of size 8 at addr ffff00001827d3b8 by task bpoc/168
Clear both pointers after freeing and test them on the paths that can still run. Poison the URBs before freeing them: usb_poison_urb() waits for a running completion handler and rejects any later submission, so after it returns the input path is quiesced and only the rawmidi trigger path can still reach bcd2000_midi_send(). No unpoison is needed; the URBs are freed on the next line.
Discovered by XBOW, triaged by Baul Lee baul.lee@xbow.com
{
"affected": [],
"aliases": [
"CVE-2026-80971"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-11T20:19:03Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: bcd2000: clear the URB pointers on disconnect\n\nbcd2000_free_usb_related_resources() frees both URBs and leaves the\npointers behind:\n\n\tusb_kill_urb(bcd2k-\u003emidi_out_urb);\n\tusb_kill_urb(bcd2k-\u003emidi_in_urb);\n\n\tusb_free_urb(bcd2k-\u003emidi_out_urb);\n\tusb_free_urb(bcd2k-\u003emidi_in_urb);\n\nThe rawmidi device outlives that call. A substream that is still open\nwhen the device is unplugged reaches bcd2000_midi_send() from the\ntrigger path on close. That function writes to the freed URB and then\nhands it to the USB core:\n\n\tbcd2k-\u003emidi_out_urb-\u003etransfer_buffer_length = BUFSIZE;\n\t...\n\tret = usb_submit_urb(bcd2k-\u003emidi_out_urb, GFP_ATOMIC);\n\nusb_kill_urb() does not stop a later submission either, so a submit that\nraces the disconnect can requeue the URB after it has been reaped.\nmidi_in_urb is exposed the same way: bcd2000_input_complete() resubmits\nit from the completion handler.\n\nKASAN on 7.2.0-rc5 (arm64):\n\n BUG: KASAN: slab-use-after-free in bcd2000_midi_send [snd_bcd2000]\n Write of size 4 at addr ffff00001827d388 by task bpoc/168\n __asan_store4\n bcd2000_midi_send [snd_bcd2000]\n bcd2000_midi_output_trigger [snd_bcd2000]\n snd_rawmidi_kernel_write1\n close_substream.part.0\n Freed by task 168:\n usb_free_urb\n bcd2000_disconnect [snd_bcd2000]\n\n BUG: KASAN: slab-use-after-free in usb_submit_urb\n Read of size 8 at addr ffff00001827d3b8 by task bpoc/168\n\nClear both pointers after freeing and test them on the paths that can\nstill run. Poison the URBs before freeing them: usb_poison_urb() waits\nfor a running completion handler and rejects any later submission, so\nafter it returns the input path is quiesced and only the rawmidi trigger\npath can still reach bcd2000_midi_send(). No unpoison is needed; the\nURBs are freed on the next line.\n\nDiscovered by XBOW, triaged by Baul Lee \u003cbaul.lee@xbow.com\u003e",
"id": "GHSA-27wq-xjr3-w8c9",
"modified": "2026-09-14T15:32:21Z",
"published": "2026-09-11T21:31:22Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-80971"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3c00004f134fc819f9d9e202c6a64acde0a1f8d0"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/459d3a64766f5ca2f1886daeaf24582831a5f5ab"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/5a77febac6faf6da40fbb4555f703eeb91b58130"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/6c07aad8a7c9ef8ebc4d03a964b882123a349a2e"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7df3194bdb7479cad9199889655a566a2c0c1d1b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9af08677aa57debaca5b57c8045c52a83d3dd376"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b06ebc7fe25a6af4a9f6e4a3d4236a4178ad4b01"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/eb482a06791d6168beb8c78cc904ac5a5ed96a55"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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