[CVE-2026-53242][MODERATE 7.0] ALSA: PCM: Fix wait queue list corruption in snd_pcm_drain() on linked streams [ Upstream

[CVE-2026-53242][MODERATE 7.0] ALSA: PCM: Fix wait queue list corruption in snd_pcm_drain() on linked streams [ Upstream

[AL-KERNEL]

CVE: CVE-2026-53242
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: ALSA: PCM: Fix wait queue list corruption in snd_pcm_drain() on linked streams [ Upstream
Commit: cac5bf3500ee6422cf64e0df0b5daeecfed42917
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cac5bf3500ee6422cf64e0df0b5daeecfed42917
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53242
Analysis date: Fri, 26 Jun 2026 06:32:24 -0400
ActionableScore: 6
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A local user with ALSA PCM access can race snd_pcm_drain() with linked stream unlinking, leaving stale wait queue entries that corrupt wait queue lists and can crash the kernel.

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ABOUT THIS REPORT
======================================================================

The original Linux kernel CVE announcement for CVE-2026-53242 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53242

The original announcement does not normally provide a security severity
estimate, CVSS assessment, or enough information to determine whether the
reported kernel bug represents a practically relevant security issue.

This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin. It combines
an autonomous classifier with LLM-assisted technical analysis and a
separate ActionableScore mechanism.

The purpose of this report is to prioritize Linux kernel CVEs before
manual review, identify cases that require prompt investigation, and
support automatic closure of issues that are unlikely to have meaningful
security impact.

Published priority for this report: MODERATE 7.0
Manual review required: YES

A detailed explanation of the methodology and priority rules is included
at the end of this message.

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AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-53242	MODERATE	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';CWE-362;*CWE-416;**CWE-476;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A race in ALSA PCM snd_pcm_drain can leave a wait entry queued on an old linked stream sleep queue after a concurrent UNLINK operation. A later drain iteration can add the same wait entry to another queue while it is still linked on the previous queue, corrupting wait queue lists and causing a later wake_up path to dereference an invalid function pointer. For the CVSS the PR:L is used because a local user or local process with access to ALSA PCM device nodes can potentially trigger drain and linked stream operations, while full administrative privileges are not inherently required in typical desktop or audio group deployments. The issue is not network reachable. Impact is at least local denial of service via kernel panic, and the paranoid score treats the wait queue list corruption as a memory safety condition that may require manual review for possible confidentiality or integrity impact.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)  SKIP CVE-2026-53242  SKIP The Fixes patch not applied yet, so unlikely that actual: 9b1dbd69ba6f8f8c69bc7b77c2ce3b9c6ed05ba6 YES  NO NO unknown 	MAYBE	DANGER INIT UAF DMAorINTERRUPT HARDWARE LINUS KPANIC 	-	-	checked

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ACTIONABLESCORE ANALYSIS
======================================================================

ActionableScore=6
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 6
* Final recommended bucket: **Actionable Moderate at minimum**

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. ALSA PCM device nodes are commonly reachable by local desktop users or users in the audio group.
* Weak or indirect corruption candidate: +1. The bug corrupts wait queue list links, but the described failure path is a NULL function pointer dereference rather than a demonstrated attacker controlled overwrite.
* Real lifetime corruption: +1. An orphaned wait entry can remain linked on an old wait queue after concurrent UNLINK, creating stale queue state across iterations.
* Reliable kernel crash / strong DoS: +1. The commit explicitly describes a subsequent wake_up leading to NULL dereference and kernel panic.
* Broad/common subsystem exposure: +1. ALSA PCM is common on desktop and workstation systems.
* Hard or unreliable race / special timing required: -1. Triggering requires a race between snd_pcm_drain() and linked stream UNLINK behavior.

Paranoid additional interpretation:

* Generic memory corruption: +2 instead of weak corruption +1. The wait queue list corruption is real kernel metadata corruption and may leave stale list entries in a sensitive wakeup path.
* Weak LPE concern: +1. There is no demonstrated privilege escalation primitive, but corrupted wait queue metadata and an invalid function pointer dereference are memory safety signals that justify manual review.

## 3. Reachability analysis

The bug is locally reachable through ALSA PCM operations involving linked streams, drain, and concurrent unlinking. Full root privileges are not inherently required if the attacker has access to relevant /dev/snd devices, which is common for logged in desktop users or members of an audio group. Containers usually do not expose ALSA devices by default, but passthrough of /dev/snd would make the path reachable inside such environments. The issue is not network reachable. Exploitation requires race timing and a specific linked stream scenario, so reliability is lower than for a simple ioctl crash.

## 4. Severity interpretation

This is stronger than an ordinary Moderate DoS because it involves actual wait queue list corruption, not just a direct NULL check failure. Realistically, the demonstrated impact is local kernel panic. Theoretical privilege escalation is not proven, but the corrupted kernel list state and stale wait entry behavior are enough to keep it in manual-review territory. It should be treated as Actionable Moderate at minimum, with Strong Important consideration only if further analysis shows controllable object lifetime or function pointer influence.

## 5. One-sentence report phrase

A local user with ALSA PCM access can race snd_pcm_drain() with linked stream unlinking, leaving stale wait queue entries that corrupt wait queue lists and can crash the kernel.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED. YES REQUIRES MANUAL CHECK.

Reason: this is a race with kernel wait queue list corruption and a possible stale lifetime condition, so it should not be auto-closed as a simple DoS without review.

======================================================================
UPSTREAM PATCH SUMMARY
======================================================================

Patch: ALSA: PCM: Fix wait queue list corruption in snd_pcm_drain() on linked streams [ Upstream
Commit: cac5bf3500ee6422cf64e0df0b5daeecfed42917
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cac5bf3500ee6422cf64e0df0b5daeecfed42917

Changed files:
  sound/core/pcm_native.c

Diff excerpt:

Not included in this email. See the upstream URL for the full patch.

Full patch:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cac5bf3500ee6422cf64e0df0b5daeecfed42917

======================================================================
DETAILED REPORT METHODOLOGY
======================================================================

The original Linux kernel CVE announcement for CVE-2026-53242 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53242

The original CVE announcement normally does not include a security-level
estimate. In particular, it may not contain a CVSS assessment, an impact
level, or enough information to determine whether the reported bug is a
practically relevant security issue. One purpose of this parallel CVE list
is to provide that missing technical and prioritization information.

The original goal of the AL-KERNEL project was to prioritize Linux kernel
CVE analysis automatically before manual review. The system can also help
identify non-security issues that may be suitable for automatic closure.

This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin.

The first analysis stage combines an autonomous classifier with additional
LLM-based analysis. The autonomous classifier runs locally on a CPU and is
based on a backpropagation neural network. Together, these mechanisms
produce a technical vulnerability description, identify likely weakness
types, estimate CVSS severity, and provide input for ActionableScore.

Two CVSS estimates are retained because incomplete kernel vulnerability
information often permits more than one defensible interpretation:

  Conservative CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7

The conservative vector represents a lower-impact interpretation.
The Best/paranoid vector intentionally represents a plausible upper-bound
interpretation and should not automatically be treated as demonstrated
real-world impact.

CVSS may also need to be adjusted for a particular Linux deployment,
because actual reachability, privileges, enabled kernel configuration,
hardware, namespaces, exposed device nodes, and other environmental
conditions can differ significantly between systems.

A separate ActionableScore mechanism evaluates practical remediation
urgency. Its analysis may include reachability, attack prerequisites,
subsystem exposure, memory-corruption characteristics, denial-of-service
reliability, and possible confidentiality, integrity, or
privilege-escalation impact.

  Conservative ActionableScore: 4
  Paranoid ActionableScore: 6

The final base severity is taken directly from the second tab-separated
field of the AL-KERNEL classification result. ActionableScore does not
replace or independently override that final AL-KERNEL decision, and
if ActionableScore adjusted impact level of ALKERNEL, then you would see
self-readable flags above like INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7.

For an AL-KERNEL result of MODERATE, this report uses the following
additional presentation split:

  ActionableScore below 5   -> MODERATE REGULAR
  ActionableScore 5 or more -> MODERATE 7.0

The distinction between MODERATE REGULAR and MODERATE 7.0 makes it
possible to identify Moderate issues that should receive manual analysis
and fixes before lower-priority MODERATE REGULAR issues. In many cases,
MODERATE REGULAR fixes may wait for a later rebase or routine update.

There is one override in which MODERATE REGULAR becomes MODERATE 7.0
even when the ActionableScore is below 5. When the AL-KERNEL result
contains the KPANIC flag, a MODERATE result is always presented as
MODERATE 7.0. The KPANIC flag selected with few regexps without
usage of AI at all, so it helps to detect cases when Kernel Crash happens
and similar (to filter False-Negative results from the LLM usage).

KPANIC indicates that a reliable kernel crash, kernel panic, or similarly
serious kernel availability impact was identified by the classification
workflow.

AL-KERNEL base severity for this report: MODERATE
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): MODERATE 7.0

These results are intended to support engineering triage. They are
machine-generated estimates, and cases marked for manual review should
be validated by a human security engineer before final disposition.
For more info read docs linked from here: https://kernelcve.org/
(and you can submit you own patch there to generate such a report
for non-existant CVE-id yet).

Note that in many cases this AI tool selects higher severity, than
real is (means you can expect Importants instead of Moderate 7.0 or
Moderates 7.0 instead of regular Moderates). If you see such cases,
please use reply email interface to add additional manual analyses
info to this particular CVE.
And please, please, let me know when you see Lows instead of Importants
or Important instead of Low (because particular for such cases I
need to tune this AI tool to make it better for this one and next similar).
My contact email for such notifications is alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).