CVE-2026-74499

Summary

In the Linux kernel, the following vulnerability has been resolved:

ALSA: usb-audio: fix OOB write in snd_usbmidi_akai_output()

snd_usbmidi_akai_output() computes its fill-loop bound

buf_end = ep->max_transfer - MAX_AKAI_SYSEX_LEN - 1;

as a signed int, so a small device-advertised bulk-OUT max_transfer makes buf_end negative. The loop guard then compares the u32 urb->transfer_buffer_length against that negative int: the usual arithmetic conversion turns buf_end into a large unsigned value, so the guard stays true and each iteration keeps appending SysEx framing and payload bytes past the end of the URB transfer buffer, which is only max_transfer bytes long.

A USB device that advertises a tiny bulk-OUT endpoint can therefore trigger an attacker-length- and content-controlled heap out-of-bounds write when a process writes to the created /dev/snd/midiCD node.

Return early when there is no room for even one SysEx, so the loop is never entered with a bound that would wrap. The loop is the last statement of the function, so bailing out is equivalent to it not running.

Discovered by XBOW, triaged by Baul Lee <baul.lee@xbow.com>

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/29a4c29943631301e85f5e9d10f25741bd78e7ba
• https://git.kernel.org/stable/c/9b22a5c8310b0d55d04f5f0159b913a2fb8b444f
• https://git.kernel.org/stable/c/b5305a0d0bb8e90a6fc9f88270d5f6c9b8c40081
• https://git.kernel.org/stable/c/2b7a0f330dd90dd1a7657cec0db019ee1efa4372
• https://git.kernel.org/stable/c/0970274613fb463d376211450cab066d34ebfe6a

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