[CVE-2026-99162][MODERATE 7.0] gpio: shared: fix use-after-free bug when adding shared proxies

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

CVE: CVE-2026-99162
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: gpio: shared: fix use-after-free bug when adding shared proxies
Commit: 8861491f8501516429e0e6c9d7a056480047227c
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8861491f8501516429e0e6c9d7a056480047227c
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99162
Analysis date: Fri, 30 Oct 2026 11:20:31 -0400
ActionableScore: 4
ActionableScore lower bound: unknown
Actionable bucket: Borderline / manual review recommended
Manual review required: YES

Summary:
A retained GPIO lookup can dereference a consumer kobject’s freed name string, causing a read-side UAF and potential kernel crash.

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

The original Linux kernel CVE announcement for CVE-2026-99162 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99162

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-2026-99162	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-99162 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=4 LEGACY=MODERATE_KPANIC RESULT=SAME V39_AEGIS_ONE_STEP_UP=MODERATE->MODERATE_KPANIC (final reconciliation agrees; DECISION: both MODERATE_KPANIC)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';*CWE-416;CWE-825;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.8';DESCR 'A shared GPIO proxy lookup stores lookup dev_id as a borrowed pointer returned by dev_name. The lookup table can outlive the consumer kobject, leaving a dangling string pointer that may be dereferenced by later GPIO lookup and string comparison operations. The demonstrated primitive is a use-after-free read that can crash the kernel. No direct out of bounds write or arbitrary write is established, although reused memory could theoretically cause an incorrect device name match and an unintended GPIO lookup association. For the CVSS the PR:L value reflects that reliable triggering requires local influence over an affected consumer device lifecycle and a later GPIO lookup, while no direct network or generic unprivileged syscall trigger is shown. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 5.8 and the production ActionableScore returned 4 with recommendation Borderline / manual review recommended. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage LOW to MODERATE_KPANIC because the manual review requirement was applied. KP and FD specialist checks stage MODERATE_KPANIC to MODERATE because KP specialist did not establish a qualifying panic. final reconciliation stage MODERATE to MODERATE_KPANIC because the cross model evidence reconciliation rule was applied. The legacy KP specialist produced a review artifact and its decision was processed by the applicable KP rules. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK and DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP and V39_AEGIS_ONE_STEP_UP and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 3.2 and ActionableScore 4 with primitive class CLASS_B 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_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4)	MAYBE	OOB INIT NOMEMCHK LEAK UAF HARDWARE  INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP KPANIC V39_AEGIS_ONE_STEP_UP MANUAL_REVIEW_REQUIRED	-	-	checked

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

ActionableScore=4
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw base score: 3.
* Conservative score: 4. Real-UAF floor 4 applied because the dangling `dev_id` is later consumed and host-admin-only triggering is not established.
* Raw paranoid score: 3.
* Paranoid score: 4. No additional technically supported exploit primitive.
* Final recommended bucket: **Borderline / manual review recommended**::

2. Signal breakdown

* +2 — Real UAF: `lookup->dev_id` borrowed `dev_name(consumer)` storage, while the lookup table can outlive the consumer kobject. The fix duplicates and later frees the string.
* +1 — Plausible kernel crash: later GPIO lookup/string comparison can dereference the freed name.
* +0 — Wrong GPIO association is only theoretical; no attacker-controlled reclaim, replacement contents, protected target, or concrete incorrect match is shown.
* +0 — No arbitrary/directed write, disclosure, authorization bypass, repeated release, or separate integrity impact.
* +0 — No extra availability point; it would duplicate the same potential crash.
* Floor: raw 3 → 4 under the real-UAF floor.
* B5-R and B3-PENDING do not apply: there is no OOB/shared-backing write.

3. Reachability analysis

The complete trigger requires creating an affected shared GPIO proxy, destroying its consumer kobject while retaining the lookup, and causing a later GPIO lookup. The supplied evidence does not establish whether an ordinary user, delegated service, or host administrator can perform that sequence. No namespace-scoped capability path, remote path, special hardware requirement, or hard timing race is proven.

4. Primitive and severity reading

This is an active lifetime violation involving a dangling pointer to the former kobject name, followed by a read during lookup processing. It is CLASS_B, but the shown stale use is a string read/comparison rather than a write, callback, refcount mutation, or attacker-shaped replacement-object consumption. Crash is plausible; useful misassociation or further corruption remains speculative. Therefore it is not presently an Important candidate and may be downgraded after review.

5. One-sentence report phrase

A retained GPIO lookup can dereference a consumer kobject’s freed name string, causing a read-side UAF and potential kernel crash.

6. Manual review advice

MANUAL CHECK RECOMMENDED

Confirm actual caller privileges and whether reclaim can produce a security-relevant false GPIO lookup match.

7. Call-site confidence

Call-site confidence: medium

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

Patch: gpio: shared: fix use-after-free bug when adding shared proxies
Commit: 8861491f8501516429e0e6c9d7a056480047227c
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8861491f8501516429e0e6c9d7a056480047227c

Commit description:

The GPIO lookup table can stay alive for longer than the kobject whose
name string's address we're assigning to lookup->dev_id. Fix a potential
UAF by duplicating the string.

Cc: stable@vger.kernel.org
Fixes: a060b8c ("gpiolib: implement low-level, shared GPIO support")
Reviewed-by: Linus Walleij <linusw@kernel.org>
Link: https://patch.msgid.link/20261014-gpio-shared-fwnode-lookup-v4-1-2253ad645fd6@oss.qualcomm.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpio/gpiolib-shared.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=8861491f8501516429e0e6c9d7a056480047227c

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

The original Linux kernel CVE announcement for CVE-2026-99162 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99162

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:L/I:L/A:H
  The Best / paranoid CVSS score: 5.8

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: 4

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).