EUVD-2026-76294
GHSA-27wq-xjr3-w8c9
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Race condition between USB disconnect and substream close warrants AC:H; local low-privileged user with open MIDI stream required, so PR:L and AV:L.
Primary rating from Vendor (Linux).
CVSS VectorVendor: Linux
Lifecycle Timeline
6DescriptionCVE.org
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>
AnalysisAI
Use-after-free in the Linux kernel ALSA bcd2000 USB MIDI driver allows a local attacker with low privileges to corrupt kernel memory, potentially achieving privilege escalation or system crash. When a BCD2000 USB device is disconnected while a MIDI rawmidi substream remains open, bcd2000_midi_send() and bcd2000_input_complete() continue to read and write previously freed URB structures, as the pointers are not nulled after usb_free_urb(). …
Unlock full vulnerability intelligence
- Risk assessment & exploitation conditions
- Attack chain visualization
- Remediation with exact patch versions
- Threat intelligence from 22 sources
- Personal watchlist & email alerts
Free forever · No credit card required
Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires: (1) the snd_bcd2000 kernel module to be loaded, which happens only when a Behringer BCD2000 USB MIDI controller is connected; (2) a local user account with sufficient permissions to open a rawmidi substream on the device (typically membership in the 'audio' group or equivalent); (3) the USB device to be physically disconnected or logically removed while the rawmidi substream is still open; (4) the rawmidi substream close path (bcd2000_midi_output_trigger) to execute after disconnect completes. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 7.8 base score (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) reflects a high-impact local privilege escalation but overstates complexity: the race condition requires a USB disconnect to be timed concurrently with an open substream close, which in practice warrants AC:H. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Upgrade to a patched Linux kernel release: 6.12.109 or later for the 6.12 stable series, 6.18.50 or later for the 6.18 stable series, 7.2.4 or later for the 7.2 stable series, or 7.3-rc1 or later for the mainline series. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, inventory Linux systems with BCD2000 USB MIDI devices connected and identify kernel versions in use. …
Sign in for detailed remediation steps and compensating controls.
Threat intelligence, references, and detailed analysis are available after sign-in.
Share
External POC / Exploit Code
Leaving vuln.today