[CVE-2026-74278][MODERATE REGULAR] ALSA: seq: Fix kernel heap address leak in bounce_error_event() [ Upstream

[CVE-2026-74278][MODERATE REGULAR] ALSA: seq: Fix kernel heap address leak in bounce_error_event() [ Upstream

[AL-KERNEL]

CVE: CVE-2026-74278
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: ALSA: seq: Fix kernel heap address leak in bounce_error_event() [ Upstream
Commit: 93d260ce43a81df579c98bee92b91316df9c1c57
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=93d260ce43a81df579c98bee92b91316df9c1c57
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74278
Analysis date: Sat, 15 Aug 2026 16:37:05 -0400
ActionableScore: 3
ActionableScore lower bound: unknown
Actionable bucket: Borderline manual review recommended / not Important
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-74278 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74278

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 REGULAR
Manual review required: YES

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

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

CVE-2026-74278	MODERATE	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N';*CWE-200;CWE-497;CWE-668;BEST CVSS score: '3.3';DESCR 'ALSA sequencer bounce error handling can expose a raw kernel heap pointer to userspace because bounce_error_event used SNDRV_SEQ_EVENT_KERNEL_ERROR with data.quote.event for both kernel and user clients. A local user client can receive the fixed length event through snd_seq_read, where the quoted pointer is copied to userspace without the variable length sanitization path. For the CVSS the PR:L is used because triggering requires a local user process with access to the ALSA sequencer interface, not remote network access. The issue is not network reachable. Impact is limited confidentiality loss through kernel heap address disclosure, which can weaken KASLR and may help a separate exploit chain, but there is no direct evidence of memory corruption, denial of service, or privilege escalation from this patch alone.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline manual review recommended / not Important (with actual score 3)	YES	OOB LEAK HARDWARE LINUS  INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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

ActionableScore=3

1. ActionableScore
* Conservative score: 3
* Paranoid score: 3
* Final recommended bucket: **Borderline manual review recommended / not Important**::

2. Signal breakdown
* Local unprivileged trigger: +1. A local user client with access to the ALSA sequencer can receive the malformed bounce event via `snd_seq_read()`.
* Confidentiality impact plausible: +1. The bug leaks a raw kernel heap pointer to userspace, weakening KASLR and potentially assisting a separate exploit chain.
* Broad/default/common subsystem exposure: +1. ALSA is common on desktop and workstation kernels, and the sequencer interface is a normal local userspace API when enabled.
* No memory corruption: +0. The patch shows pointer disclosure only, not UAF, OOB write, double free, refcount misuse, or object corruption.
* No privilege escalation primitive: +0. LPE is only an indirect possibility if combined with another bug.

3. Reachability analysis
A local userspace process can trigger the issue if it can access the ALSA sequencer device. This is not network reachable. Containers and sandboxes may reduce exposure if `/dev/snd/seq` is not passed through. On desktop systems the interface may be reachable by ordinary logged-in users, while on hardened servers ALSA or sequencer access may be absent.

4. Severity interpretation
This behaves like an ordinary Moderate or Low-like information disclosure, not an Important-class kernel memory corruption issue. The realistic impact is kernel heap address disclosure. Theoretical risk is that the leak can help bypass KASLR in a separate exploit chain, but the patch does not support direct privilege escalation, integrity impact, or DoS.

5. One-sentence report phrase
A local ALSA sequencer user can receive a bounce error event that exposes a raw kernel heap pointer through `snd_seq_read()`, causing limited confidentiality impact by weakening KASLR but not directly enabling memory corruption or privilege escalation.

6. Manual review recommendation
MANUAL CHECK RECOMMENDED.
Reason: the standalone score is low, but concrete kernel pointer leaks are useful exploit-chain aids and should not be blindly auto-closed without confirming product exposure to `/dev/snd/seq`.

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

Patch: ALSA: seq: Fix kernel heap address leak in bounce_error_event() [ Upstream
Commit: 93d260ce43a81df579c98bee92b91316df9c1c57
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=93d260ce43a81df579c98bee92b91316df9c1c57

Changed files:
  sound/core/seq/seq_clientmgr.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=93d260ce43a81df579c98bee92b91316df9c1c57

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

The original Linux kernel CVE announcement for CVE-2026-74278 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74278

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: Not available
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
  The Best / paranoid CVSS score: 3.3

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: 3

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: NO
Published priority for this report (same as in Subject): MODERATE REGULAR

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).