CVE-2026-80971
Received
Received - Intake
Use-After-Free in ALSA bcd2000 USB MIDI Driver
Vulnerability report for CVE-2026-80971, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-09-11
Last updated on: 2026-09-11
Assigner: kernel.org
Description
Description
In 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>
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
Currently, no data is known.
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-UNKNOWN |
