[CVE-2026-74261][LOW] ALSA: seq: avoid stale FIFO cells during resize [ Upstream

[CVE-2026-74261][LOW] ALSA: seq: avoid stale FIFO cells during resize [ Upstream

[AL-KERNEL]

CVE: CVE-2026-74261
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: ALSA: seq: avoid stale FIFO cells during resize [ Upstream
Commit: 98a965cb1e767b54b6bbd831b6cea26f521a8f51
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=98a965cb1e767b54b6bbd831b6cea26f521a8f51
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74261
Analysis date: Sat, 15 Aug 2026 06:32:26 -0400
ActionableScore: 2
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-74261 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74261

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: LOW
Manual review required: NO

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-2026-74261	LOW	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-362;CWE-667;**CWE-400;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'ALSA sequencer FIFO resize has a race where an event cell allocated or dequeued from the old pool can be relinked after f pool is swapped to a replacement pool. This stale old pool cell can remain outside the drained oldhead list and keep the old pool counter elevated, causing snd_seq_pool_delete to wait in the resize ioctl. For the CVSS the PR:L because a local user or process needs access to ALSA sequencer operations and the resize path, but full administrator privileges are not normally required on systems that expose /dev/snd/seq to users. The issue is not network reachable and requires a timing window between resize and event enqueue or putback paths, so AC:H is used. Impact is denial of service through a blocked resize and retained pool references, with no concrete evidence of UAF after free, information disclosure, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)	YES	LOCK INIT RACE HARDWARE LINUS 	NO	NO	checked

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

ActionableScore=2

1. ActionableScore
* Conservative score: 2
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**::

2. Signal breakdown
* Local unprivileged trigger: +1. ALSA sequencer operations may be reachable by local users on systems exposing `/dev/snd/seq`.
* Reliable kernel crash / strong DoS: +1. The demonstrated impact is a blocked resize ioctl waiting in `snd_seq_pool_done`, not proven kernel memory corruption.
* Hard or unreliable race / special timing required: -1. The issue requires a timing window between FIFO resize and event enqueue or putback paths.
* Broad/default/common subsystem: +1. ALSA sequencer is a common local multimedia subsystem, though not usually relevant on minimal servers.
* No memory corruption or LPE signal awarded. The stale old-pool cell keeps the old pool counter elevated, but the patch does not show UAF-after-free, controlled reclaim, type confusion, callback control, or writable stale object access.

3. Reachability analysis
A local user or process with access to ALSA sequencer ioctls can potentially trigger the race by resizing the FIFO while another path queues or puts back event cells. Containers usually need access to the host sound device, so container reachability depends on device passthrough. The path is not network reachable. Exploitation requires concurrency and timing, and the demonstrated failure is a local hang in the pool teardown path rather than a host-wide crash or privilege boundary bypass.

4. Severity interpretation
This behaves like an ordinary Moderate or Low-like local DoS. The theoretical concern is a lifetime/race bookkeeping error around stale FIFO cells, but realistic evidence points to a retained pool reference and blocked teardown only. There is no supported privilege escalation primitive and no confidentiality or integrity impact.

5. One-sentence report phrase
A race in ALSA sequencer FIFO resizing can relink stale old-pool cells after the pool swap, leaving the retired pool counter elevated and causing a local resize ioctl to block in pool teardown.

6. Manual review recommendation
NO MANUAL CHECK NEEDED. The issue is local, race-dependent, DoS-only based on the patch and reproducer, with no concrete memory corruption or privilege escalation primitive.

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

Patch: ALSA: seq: avoid stale FIFO cells during resize [ Upstream
Commit: 98a965cb1e767b54b6bbd831b6cea26f521a8f51
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=98a965cb1e767b54b6bbd831b6cea26f521a8f51

Changed files:
  sound/core/seq/seq_fifo.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=98a965cb1e767b54b6bbd831b6cea26f521a8f51

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

The original Linux kernel CVE announcement for CVE-2026-74261 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74261

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:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

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: unknown
  Paranoid ActionableScore: 2

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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

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).