linux-cve-announce - CVE-2026-23191: ALSA: aloop: Fix racy access at PCM trigger

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Message-ID: <2026021433-CVE-2026-23191-f990@gregkh>
Date: Sat, 14 Feb 2026 17:28:48 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2026-23191: ALSA: aloop: Fix racy access at PCM trigger

From: Greg Kroah-Hartman <gregkh@...nel.org>

Description
===========

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

ALSA: aloop: Fix racy access at PCM trigger

The PCM trigger callback of aloop driver tries to check the PCM state
and stop the stream of the tied substream in the corresponding cable.
Since both check and stop operations are performed outside the cable
lock, this may result in UAF when a program attempts to trigger
frequently while opening/closing the tied stream, as spotted by
fuzzers.

For addressing the UAF, this patch changes two things:
- It covers the most of code in loopback_check_format() with
  cable->lock spinlock, and add the proper NULL checks.  This avoids
  already some racy accesses.
- In addition, now we try to check the state of the capture PCM stream
  that may be stopped in this function, which was the major pain point
  leading to UAF.

The Linux kernel CVE team has assigned CVE-2026-23191 to this issue.


Affected and fixed versions
===========================

	Fixed in 6.12.70 with commit bad15420050db1803767e58756114800cce91ea4
	Fixed in 6.18.10 with commit 5727ccf9d19ca414cb76d9b647883822e2789c2e
	Fixed in 6.19 with commit 826af7fa62e347464b1b4e0ba2fe19a92438084f

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-23191
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	sound/drivers/aloop.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/bad15420050db1803767e58756114800cce91ea4
	https://git.kernel.org/stable/c/5727ccf9d19ca414cb76d9b647883822e2789c2e
	https://git.kernel.org/stable/c/826af7fa62e347464b1b4e0ba2fe19a92438084f