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

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Summary

CVECVE-2026-80973
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-11 20:19:03 UTC
Updated2026-09-11 20:19:03 UTC
DescriptionIn 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 <[email protected]>

Risk And Classification

EPSS: 0.002000000 probability, percentile 0.099340000 (date 2026-09-13)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected c6d43ba816d1cf1d125bfbfc938f2a28a87facf9 466e911bbbbb779bb06337e35a286e5ca7af16b3 git Not specified
CNA Linux Linux affected c6d43ba816d1cf1d125bfbfc938f2a28a87facf9 2a6f6fba3bd31d2e8c957fefa29156e35e5e75d5 git Not specified
CNA Linux Linux affected c6d43ba816d1cf1d125bfbfc938f2a28a87facf9 34816e2cfeabafb8eccf54687186ce25699e8363 git Not specified
CNA Linux Linux affected c6d43ba816d1cf1d125bfbfc938f2a28a87facf9 a478893b59e36cfe7d77a76b352f2db55502e879 git Not specified
CNA Linux Linux affected 2.6.39 Not specified
CNA Linux Linux unaffected 2.6.39 semver Not specified
CNA Linux Linux unaffected 6.12.109 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.50 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.4 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/466e911bbbbb779bb06337e35a286e5ca7af16b3 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/a478893b59e36cfe7d77a76b352f2db55502e879 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/2a6f6fba3bd31d2e8c957fefa29156e35e5e75d5 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/34816e2cfeabafb8eccf54687186ce25699e8363 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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