[CVE-2026-98668][MODERATE REGULAR] iio: buffer: Ensure bounce buffer used for unaligned case is zeroed.

[CVE-2026-98668][MODERATE REGULAR] iio: buffer: Ensure bounce buffer used for unaligned case is zeroed.

[AL-KERNEL]

CVE: CVE-2026-98668
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: iio: buffer: Ensure bounce buffer used for unaligned case is zeroed.
Commit: b5c2f21f645e40c70fda2a4283e6f2a81e5cb9f2
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b5c2f21f645e40c70fda2a4283e6f2a81e5cb9f2
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98668
Analysis date: Mon, 19 Oct 2026 01:21:53 -0400
ActionableScore: 2
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
An uninitialized padding leak in timestamped unaligned IIO samples can expose a small amount of stale kernel heap data to a local process that can read the affected IIO buffer.

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

The original Linux kernel CVE announcement for CVE-2026-98668 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98668

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: NO

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

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

CVE-2026-98668	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98668 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=1 LEGACY=MODERATE RESULT=DIFF V39_AEGIS_ONE_STEP_UP=LOW->MODERATE TEMP_DISTANCE_MERGE_SKIP=AEGIS_NO_POSITIVE_SEVERITY_EVIDENCE (final Legacy and Aegis differ; FINAL: MODERATE, Aegis: MODERATE_KPANIC)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N';CWE-908;*CWE-200;*CWE-457;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N';BEST CVSS score: '5.5';DESCR 'An information disclosure in the IIO buffered data path occurs because iio_push_to_buffers_with_ts_unaligned can expose uninitialized heap padding when the sample data size is not a multiple of 8 and timestamps are enabled. A local process able to read the affected IIO buffer may receive stale kernel heap bytes located between the sample data and its timestamp. For the CVSS the PR:L value is used because triggering requires a local user context with permission to access the IIO buffer device. The issue is not directly network reachable. Impact is limited to confidentiality because the available primitive is an uninitialized memory disclosure rather than a write, UAF, or kernel crash. A single sample likely exposes only a small amount of padding, but repeated samples may disclose different stale heap contents and justify manual review of the worst case confidentiality impact. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 5.5 and the production ActionableScore returned 2 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were final reconciliation stage LOW to MODERATE because KP specialist did not establish a qualifying panic and the cross model evidence reconciliation rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were KPANIC_UNSUPPORTED_REMOVED and V39_AEGIS_ONE_STEP_UP and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 3.3 and ActionableScore 1 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is MODERATE.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2)	MAYBE	SIMPLEFIX LEAK KPANIC_UNSUPPORTED_REMOVED V39_AEGIS_ONE_STEP_UP MANUAL_REVIEW_REQUIRED	-	-	checked

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

ActionableScore=2
PrimitiveClass=CLASS_B
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw conservative score: 2
* Conservative score: 2
* Raw paranoid score: 2
* Paranoid score: 2
* No floor or cap was applied.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +1 Confidentiality plausible. Uninitialized heap padding is copied through the IIO buffer to userspace, establishing a concrete disclosure path.
* +1 Practical exploit chain. The sequence from uninitialized bounce-buffer padding to userspace-visible timestamped samples is directly established.
* No local-unprivileged bonus. Reading the IIO device is established, but the supplied evidence does not resolve device-node permissions or prove ordinary-user access.
* No substantial-disclosure or strong-leverage bonus. At most seven padding bytes appear exposed per affected layout, and varying sensitive contents across repeated reads are not demonstrated.
* No integrity or availability points. There is no write primitive, UAF, OOB access, crash, or persistent resource exhaustion.
* No authorization-bypass signal. B4-PENDING and B4 review profiles do not apply.
* NEW52 B5-R does not apply because there is no heap OOB write or retry-accumulated offset.
* NEW53 B3-PENDING does not apply because no shared-backing write exists.
* V32, V33, and V34 do not apply because no skb checksum metadata or active structured-state corruption exists.

3. Reachability analysis

The vulnerable kernel path produces timestamped IIO samples whose data length is not aligned to eight bytes. A local process must be able to read the corresponding IIO buffer, but the supplied patch does not establish whether that access is available to an ordinary user, a delegated service, or only an administrator.

An enabled timestamp and a device or driver using `iio_push_to_buffers_with_ts_unaligned()` are prerequisites. No network trigger, namespace-capability path, special retry sequence, or race is involved. Prior device configuration may be required, but the evidence does not establish who controls it. Therefore host-administrator and namespace-scoped privilege requirements remain unresolved.

4. Primitive and severity interpretation

The exact primitive is a bounded disclosure of uninitialized heap padding to userspace. It is not an OOB read because the bytes are within the allocated bounce buffer, but they were not initialized before being exported.

This is CLASS_B as a concrete but constrained kernel information-disclosure primitive. It is not CLASS_A because substantial disclosure, attacker-selected kernel addresses, sensitive-object targeting, or a reliable stream of varying heap contents is not established.

The demonstrated consequence is disclosure of stale heap bytes. Potential disclosure of pointers or other sensitive fragments is plausible but unresolved. Repeated exposure does not by itself prove that different heap contents can be harvested.

ImportantCandidate is NO because the patch does not establish substantial disclosure or another Important-preserving primitive. AutoDowngradeAllowed is YES because the disclosure is bounded and no unresolved corruption, authorization, ownership, or cross-boundary write primitive remains. Operational severity is Low to Moderate, depending primarily on IIO device permissions and whether repeated reallocations expose changing data.

5. One-sentence report phrase

An uninitialized padding leak in timestamped unaligned IIO samples can expose a small amount of stale kernel heap data to a local process that can read the affected IIO buffer.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Confirm device-node permissions, affected drivers and sample layouts, maximum padding size, whether buffer reallocations expose changing heap contents, and whether sensitive kernel data can realistically appear in the leaked bytes.

7. Call-site confidence

Call-site confidence: medium

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

Patch: iio: buffer: Ensure bounce buffer used for unaligned case is zeroed.
Commit: b5c2f21f645e40c70fda2a4283e6f2a81e5cb9f2
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b5c2f21f645e40c70fda2a4283e6f2a81e5cb9f2

Commit description:

iio_push_to_buffers_with_ts_unaligned() leaks uninitialized heap memory
to userspace if the data passed in is not a multiple of 8 bytes and the
timestamp is enabled. Specify __GFP_ZERO for the devm_krealloc()
to ensure any extra space is cleared.

Fixes: 95ec3fd ("iio: core: Introduce iio_push_to_buffers_with_ts_unaligned()")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://sashiko.dev/#/patchset/20260529121005.1470-1-kimjinseob88%40gmail.com
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Reviewed-by: Joshua Crofts <joshua.crofts1@gmail.com>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/iio/industrialio-buffer.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=b5c2f21f645e40c70fda2a4283e6f2a81e5cb9f2

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

The original Linux kernel CVE announcement for CVE-2026-98668 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98668

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:L/PR:L/UI:N/S:U/C:L/I:N/A:N
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
  The Best / paranoid CVSS score: 5.5

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: 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).