[CVE-2026-64001][MODERATE 7.0] ALSA: pcm: oss: Fix setup list UAF on proc write error [ Upstream

[AL-KERNEL <alkernel@kernelcve.org>]

CVE: CVE-2026-64001
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: ALSA: pcm: oss: Fix setup list UAF on proc write error [ Upstream
Commit: 8be4efd0dc0093eb7a02ad1aac936bca2a1f04ce
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8be4efd0dc0093eb7a02ad1aac936bca2a1f04ce
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64001
Analysis date: Sun, 19 Jul 2026 23:12:05 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A local UAF in ALSA PCM OSS setup handling can leave a freed setup entry linked after a proc write allocation failure, allowing a later OSS open to dereference stale kernel memory and crash the system.

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

The original Linux kernel CVE announcement for CVE-2026-64001 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64001

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
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CVE-2026-64001	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	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-416;*CWE-672;*CWE-664;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'snd_pcm_oss_proc_write can publish a newly allocated setup entry on setup_list before task name allocation completes. If that allocation fails, the error path frees an entry that remains linked, and a later OSS device open can walk the stale list entry in snd_pcm_oss_look_for_setup and dereference freed memory. For the CVSS the PR:L is selected for the paranoid score because a local unprivileged process may reach the proc write path on systems where ALSA OSS proc controls are writable or delegated, while stricter deployments may map this to PR:H. The issue is not network reachable and requires local interaction with ALSA OSS proc state. Impact is at least a local denial of service via kernel crash and in worst case may allow confidentiality or integrity impact due to a linked list UAF candidate. For the paranoid score, choose the highest still-defensible interpretation supported by the bug class and patch context, with preference for manual-review sensitivity over autoclosed false negatives.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)  SKIP CVE-2026-64001 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	WRITE OOB INIT NOMEMCHK ERRORPATH UAF HARDWARE LINUS SYZBOT KPANIC 	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. The affected path is local ALSA OSS proc interaction plus later OSS device open. Practical permissions may vary by distro and device node or proc entry policy.
* Generic memory corruption: +2. The patch fixes a real UAF pattern where a freed `snd_pcm_oss_setup` remains linked in `setup_list`.
* Real lifetime corruption: +1. The bug is specifically stale pointer after free in a kernel linked list.
* Reliable kernel crash / strong DoS: +1. Later list traversal can dereference freed memory.
* Hard or unreliable trigger condition: -1. Triggering requires `kstrdup()` allocation failure after the entry was linked.
* Legacy / non-default execution mode: -1. ALSA PCM OSS compatibility is a legacy path and may not be enabled or exposed on all systems.

Paranoid additional interpretation:

* Paranoid score keeps the issue at 5 because this is a linked-list UAF in kernel memory, but without demonstrated attacker-controlled reclaim, object replacement, write-after-free, callback dispatch, or type confusion.
* No separate LPE bonus is awarded. A UAF exists, but the patch evidence mainly supports stale dereference and crash, not a concrete privilege-escalation primitive.

## 3. Reachability analysis

A local user or local process that can write the relevant ALSA OSS proc setup entry may trigger the bad error path, and a later OSS device open can traverse the stale `setup_list` entry. This is not network reachable. Namespace or container impact depends on whether ALSA device nodes and proc controls are delegated into the container. In stricter deployments, access may require elevated local privileges or device-specific permissions, but in permissive desktop or audio-enabled environments local reachability is plausible.

Call-site confidence: high. The commit message explicitly identifies the producer path `snd_pcm_oss_proc_write()` and the later consumer path `snd_pcm_oss_look_for_setup()`.

## 4. Severity interpretation

This is more than an ordinary low-risk cleanup because the freed object remains published in a kernel list and is later dereferenced. Realistic impact is local DoS through kernel crash, with high complexity due to needing an allocation failure at the right point. Theoretical memory-corruption risk exists because it is a UAF, but the provided patch does not show controlled reclaim, overwrite, callback control, or type confusion. Therefore it is best treated as Actionable Moderate, not automatically Important.

## 5. One-sentence report phrase

A local UAF in ALSA PCM OSS setup handling can leave a freed setup entry linked after a proc write allocation failure, allowing a later OSS open to dereference stale kernel memory and crash the system.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is a real kernel lifetime bug and linked-list UAF. Even though demonstrated impact is mainly DoS and exploitation requires an allocation-failure path, UAF issues should not be auto-closed without manual review.

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

Patch: ALSA: pcm: oss: Fix setup list UAF on proc write error [ Upstream
Commit: 8be4efd0dc0093eb7a02ad1aac936bca2a1f04ce
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8be4efd0dc0093eb7a02ad1aac936bca2a1f04ce

Changed files:
  sound/core/oss/pcm_oss.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=8be4efd0dc0093eb7a02ad1aac936bca2a1f04ce

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

The original Linux kernel CVE announcement for CVE-2026-64001 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64001

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: 5

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).