CVE-2026-74500

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

ALSA: usb-audio: fix stack info leak in RME Digiface status

snd_rme_digiface_read_status() reads a four-word status block from the device into an uninitialised on-stack __le32 buf[4] and, whenever the vendor control-IN transfer does not return a negative error, copies all four words into the callers status[].

snd_usb_ctl_msg() copies the full requested size back into the callers buffer regardless of how many bytes the data stage actually delivered:

buf = kmemdup(data, size, GFP_KERNEL);
err = usb_control_msg(dev, pipe, request, requesttype,
		      value, index, buf, size, timeout);
memcpy(data, buf, size);

usb_control_msg() returns the transferred length on a short control-IN, which is a non-negative value, and writes only that many bytes. The remainder of the copy back is the kmemdup()ed image of the callers buffer, so a device answering with a short data stage leaves the trailing words of buf[] holding leftover kernel stack. The only guard in the caller is err < 0, so those words are stored into status[].

They then reach user space: snd_rme_digiface_get_status_val() selects a 16-bit halfword of status[] per the controls reg/mask, and the eight Digiface status controls together expose the whole 16-byte frame to an unprivileged reader of /dev/snd/controlC*.

Zero-initialise the buffer so a short read yields zeros instead of stack residue. This mirrors snd_rme_get_status1(), which already clears its output word before the same kind of vendor read.

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

Affected Software

References

• https://git.kernel.org/stable/c/441aaad150c57edaf57ee482a79a3bf4c5b7e353
• https://git.kernel.org/stable/c/7ba01e0d3539d9cf0aef3e82938f1648147744cc
• https://git.kernel.org/stable/c/98dbfbb38e297c25c5b0af4a9018d71ac25e8554
• https://git.kernel.org/stable/c/b3a346d5c99dd73cf84711f2a43e42691990efd2