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CVE-2026-80971
ALSA: bcd2000: clear the URB pointers on disconnect
Published 2026-09-11 (37 days ago) by the Linux kernel CNA. Subsystem sound/usb. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-80971 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | fixedDLA-4841-1 · 2026-10-17 · text | 6.1.190-1 | Update the kernel and reboot. DLA-4841-1 shipped the fix on 2026-10-17, in 6.1.190-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6528-1 · 2026-09-29 · text | 6.12.111-1 | Update the kernel and reboot. DSA-6528-1 shipped the fix on 2026-09-29, in 6.12.111-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4817-1 · 2026-10-04 · text | 6.12.111-1~deb12u1 | Update the kernel and reboot. DLA-4817-1 shipped the fix on 2026-10-04, in 6.12.111-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
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>
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
sound/usb/bcd2000/bcd2000.c
- What this is
- SOUNDMAINTAINERS section matched on sound/ · linux-sound@vger.kernel.org · Maintained
- Kernel module
- snd_bcd2000
Check it on the machine
grep -wE 'CONFIG_SND|CONFIG_SND_BCD2000' /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
lsmod | grep -w snd_bcd2000Prints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.
- bookworm, trixie, forky, sid, bookworm · linux-6.12Mnot built on amd64/cloud-amd64, arm64/cloud-arm64
- M
- a module where it is built at all; some flavours do not build it
- Build switches
- CONFIG_SND, CONFIG_SND_BCD2000
- Reads as
- all on means the file is compiled; any one off means it is not.
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-09-11 (37 days ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.16%, higher than 5.2% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- sound/usb
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 3.16 | 5.10.270 | 9af08677aa57 |
| 3.16 | 5.15.221 | 5a77febac6fa |
| 3.16 | 6.1.188 | 3c00004f134f |
| 3.16 | 6.6.157 | 6c07aad8a7c9 |
| 3.16 | 6.12.109 | eb482a06791d |
| 3.16 | 6.18.50 | 7df3194bdb74 |
| 3.16 | 7.2.4 | b06ebc7fe25a |
| 3.16 | 7.3 | 459d3a64766f |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4841-1 | 2026-10-17 | bookworm 6.1.190-1 | tracker |
| DLA-4817-1 | 2026-10-04 | bookworm 6.12.111-1~deb12u1 | tracker |
| DSA-6528-1 | 2026-09-29 | trixie 6.12.111-1 | tracker |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The UAF is reached locally by USBDEVFS_DISCONNECT (or sysfs unbind) on an already-bound Behringer BCD2000 while /dev/snd/midi* is held, then close; there is no network or packet path. This matches AV:L scoring of analogous USB disconnect UAFs (CVE-2025-40283, CVE-2026-64585); physical unplug is only an extra path.
- AC:LAttack complexity, low
- The attacker opens the rawmidi node, optionally enables active sensing, then issues USBDEVFS_DISCONNECT and close; close_substream deterministically writes the freed URB in bcd2000_midi_send(). Concurrent write versus disconnect is also attacker-driven. No uncontrollable race or layout is required to trigger the UAF.
- PR:LPrivileges required, low
- USBDEVFS_DISCONNECT has no capable() check, only write access to /dev/bus/usb that udev uaccess/plugdev rules grant seat users, and snd_rawmidi_open has no capability gate on /dev/snd/midi*. An unprivileged local account suffices; init-namespace root is not required.
- UI:NUser interaction, none
- The attacker performs open, disconnect, and close on their own fds against an already-attached BCD2000 (DJ workstation/kiosk). No separate victim action such as plugging a device or clicking is required during exploitation.
- S:UScope, unchanged
- The slab use-after-free of struct urb and the subsequent usb_submit_urb run entirely in the host kernel. This is ordinary local privilege escalation, not a VM, IOMMU, or sandbox boundary escape.
- C:HConfidentiality impact, high
- KASAN shows a use-after-free read in usb_submit_urb of the dangling midi_out_urb after usb_free_urb. Reclaiming the URB slab lets the attacker supply URB fields that the USB core then reads, enabling kernel disclosure, as with other heap UAFs.
- I:HIntegrity impact, high
- bcd2000_midi_send() writes transfer_buffer_length on the freed URB and then submits it. A reclaimed fake URB plus usb_submit_urb is a heap write and control-flow primitive (completion handler/DMA setup) suitable for hijack, so integrity impact is High.
- A:HAvailability impact, high
- The UAF oopses the kernel (KASAN slab-use-after-free in bcd2000_midi_send and usb_submit_urb). The attacker can repeat connect/disconnect to crash on demand, so availability impact is High.