CVE-2026-74278

What the bug is

The comment above bounce_error_event() documents that user clients should receive SNDRV_SEQ_EVENT_BOUNCE with the original event embedded as variable-length data, while kernel clients should receive SNDRV_SEQ_EVENT_KERNEL_ERROR with a quoted kernel pointer. However, the implementation unconditionally uses SNDRV_SEQ_EVENT_KERNEL_ERROR with data.quote.event set to the raw struct snd_seq_event pointer for all clients. When a bounce error event is delivered to a USER_CLIENT via snd_seq_read(), the kernel heap address in data.quote.event is exposed to userspace through copy_to_user() in the fixed-length branch. This is a distinct leak path from the one addressed by commit 705dd6dcbc0e ("ALSA: seq: Clear variable event pointer on read"), which sanitizes data.ext.ptr in the variable-length branch of snd_seq_read(). The bounce_error_event() leak uses fixed-length events that take the else branch where no sanitization occurs. Differentiate the bounce event by client type. For USER_CLIENT, send SNDRV_SEQ_EVENT_BOUNCE with SNDRV_SEQ_EVENT_LENGTH_VARIABLE and data.ext pointing to the original event. The variable-length path in snd_seq_event_dup() copies the event data into chained cells, and snd_seq_expand_var_event() copies only the content -- never the pointer -- to userspace. For KERNEL_CLIENT, keep the existing SNDRV_SEQ_EVENT_KERNEL_ERROR behavior with the quoted pointer.

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/core/seq/seq_clientmgr.c

What this is

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

Kernel module

snd_seq

Check it on the machine

grep -wE 'CONFIG_SND|CONFIG_SND_SEQUENCER' /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_seq

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, sidMnot 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_SEQUENCER

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

2026-08-15 (2 months ago)source

CVSS

no vector published, unrated

Attack vector

not published

EPSS

0.17%, higher than 5.7% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

not yet assignedsource

Subsystem

sound/core

Upstream fixes

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

Introduced	Fixed in	Commit
2.6.12	6.12.97	93d260ce43a8
2.6.12	6.18.40	dae23c545eb5
2.6.12	7.1.5	0527a56cb327
2.6.12	7.2	efc86691e4d8