High [CVE-2026-74499] fix OOB write in snd_usbmidi_akai_output

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/midiC*D* 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 A flaw was found in the kernel's Advanced Linux Sound Architecture (ALSA) USB audio driver.

Affected products named by the advisory: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 7; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9; and 1 more.