CVE-2026-74682

What the bug is

data_ep_set_params() sizes each URB transfer buffer before it adds the Format Type II transfer delimiter: u->packets = urb_packs; u->buffer_size = maxsize * u->packets; if (fmt->fmt_type == UAC_FORMAT_TYPE_II) u->packets++; /* for transfer delimiter */ u->urb = usb_alloc_urb(u->packets, GFP_KERNEL); buffer_size is computed from the pre-increment packet count and never recomputed, so for a Type II endpoint the buffer is one packet short of the packet count the URB is built with. prepare_inbound_urb() then lays out one iso frame per packet and never consults buffer_size: offs = 0; for (i = 0; i < urb_ctx->packets; i++) { urb->iso_frame_desc[i].offset = offs; urb->iso_frame_desc[i].length = ep->curpacksize; offs += ep->curpacksize; } urb->transfer_buffer_length = offs; urb->number_of_packets = urb_ctx->packets; The last descriptor therefore points one packet past the end of the transfer buffer, where the host controller writes device data on every inbound transfer. prepare_silent_urb() and prepare_playback_urb() bound their fill loops by ctx->buffer_size, so only capture is affected. fmt_type comes from the device's audio streaming descriptors, so any device advertising a Type II capture format hits this once userspace sets hw_params on the stream. KASAN on 7.2.0-rc5 (arm64) with a dummy_hcd/raw-gadget device, one report per inbound transfer: BUG: KASAN: slab-out-of-bounds in dummy_timer Write of size 64 at addr ffff0000186171c0 by task cons02/166 __asan_memcpy dummy_timer hrtimer_run_softirq Allocated by task 166: usb_alloc_coherent snd_usb_endpoint_set_params The buggy address is located 0 bytes to the right of allocated 64-byte region [ffff000018617180, ffff0000186171c0) Compute buffer_size after the delimiter packet has been accounted for, and bound the fill loop by buffer_size, as prepare_silent_urb() already does on the outbound side. This grows every Type II URB allocation by one maxsize packet. Discovered by XBOW, triaged by Baul Lee <baul.lee@xbow.com>

Where it lives

The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.

sound/usb/endpoint.c

What this is

SOUNDMAINTAINERS section matched on sound/ · linux-sound@vger.kernel.org · Maintained

Kernel module

snd_usb_audio

Check it on the machine

grep -wE 'CONFIG_SND|CONFIG_SND_USB_AUDIO' /boot/config-$(uname -r)

Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.

lsmod | grep -w snd_usb_audio

Prints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.

Show whether Debian builds this, per release

Debian builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.

• bookworm, trixie, forky, sid, bookworm · linux-6.12Mnot built on amd64/cloud-amd64, arm64/cloud-arm64

M

a module where it is built at all; some flavours do not build it

Build switches

CONFIG_SND, CONFIG_SND_USB_AUDIO

Reads as

all on means the file is compiled; any one off means it is not.

From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages

Signals

Published

2026-08-22 (2 months ago)source

CVSS

no vector published, unrated

Attack vector

not published

EPSS

0.18%, higher than 6.8% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

not yet assignedsource

Subsystem

sound/usb

Upstream fixes

The versions the CNA records as introducing and fixing this, and the commit for each. source

Introduced	Fixed in	Commit
3.5	5.10.265	6af5f29af771
3.5	5.15.216	f1fbb50b9931
3.5	6.1.183	137bf034740e
3.5	6.6.152	6607f8524257
3.5	6.12.104	ca22c94bdfc2
3.5	6.18.45	0a235379825e
3.5	7.1.9	d3ed4e6321bb
3.5	7.2	69ee44e1a23b

Debian advisories