CVE-2026-74339

What the bug is

snd_seq_read() copies a queued variable-length event header to userspace before expanding the payload. Queued variable-length events use SNDRV_SEQ_EXT_CHAINED internally, and data.ext.ptr points at the first extension cell. The read side strips SNDRV_SEQ_EXT_* bits from data.ext.len before the copy, but it leaves data.ext.ptr untouched. A userspace sequencer client can therefore write a direct variable event to itself and read back the extension-cell kernel address from the returned header. Clear the temporary header pointer before copy_to_user(). The original queued event remains unchanged and is still passed to snd_seq_expand_var_event(), so payload expansion keeps using the internal chain.

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

0.21%, higher than 11.0% 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	5.15.212	14fe4f75fd53
2.6.12	6.1.178	f29243c21192
2.6.12	6.6.145	e0c3edd86414
2.6.12	6.12.97	6b52211eba21
2.6.12	6.18.40	74ac1ce1f4af
2.6.12	7.1.5	c2ac9287e899
2.6.12	7.2	705dd6dcbc0e