[CVE-2026-98501][MODERATE 7.0] HID: alps: fix use-after-free on input2 registration failure

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

CVE: CVE-2026-98501
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: HID: alps: fix use-after-free on input2 registration failure
Commit: 64f824dccfd316fd3db8ea1cc4e8a76ad6a02740
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=64f824dccfd316fd3db8ea1cc4e8a76ad6a02740
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98501
Analysis date: Sat, 24 Oct 2026 07:28:48 -0400
ActionableScore: 4
ActionableScore lower bound: unknown
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
A registration-failure race leaves a freed input device reachable from active HID report processing, causing a host-kernel UAF with unresolved post-free input-state effects.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-98501 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98501

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-2026-98501	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98501 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=5 LEGACY=MODERATE_KPANIC RESULT=SAME (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:H/I:H/A:H';*CWE-416;CWE-362;*CWE-664;Other CVSS 'AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A registration failure can leave data input2 pointing to a freed input_dev while HID URBs remain active. A U1_SP_ABSOLUTE_REPORT_ID can then enter u1_raw_event and pass the stale object to input reporting operations, providing a concrete use after free dereference with potential stale object writes. For the CVSS the PR:L value reflects the paranoid local exploitation case where a local user would need to influence memory pressure and allocator reuse. Reliable exploitation also depends on an uncommon registration failure, precise report timing, and useful object reuse. The demonstrated impact is a kernel crash, while controlled reuse may plausibly affect confidentiality and integrity or permit privilege escalation. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 7 and the production ActionableScore returned 4 with recommendation Actionable Moderate / Strong Important candidate requiring manual review. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. No severity changing production threshold or specialist override was recorded. 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. The independent weaker Aegis shadow evaluated CVSS 2.0 and ActionableScore 5 with primitive class CLASS_B and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 4)	MAYBE	USB INIT UAF HARDWARE LINUS KPANIC 	-	-	checked

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

1. ActionableScore

* Raw base score: 3.
* Conservative score: 4. Real-UAF floor 4 applied: 3 -> 4.
* Raw paranoid score: 3.
* Paranoid score: 4. Same floor; no unsupported reclaim or LPE bonus.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

* +2 — Real UAF: failed `input_register_device()` frees `input2` while `data->input2` remains stale.
* +1 — Reliable kernel crash/strong DoS is plausible when `u1_raw_event()` passes the freed active `input_dev` into input-reporting operations.
* +1 — Firmware/device-mediated influence: an HID report reaches the stale use while URBs are active.
* -1 — A registration failure plus report arrival in the failure window is a specifically narrow timing condition.
* Raw arithmetic: 2 + 1 + 1 - 1 = 3.
* Floor 4 applies because this is active structured `input_dev` state used by runtime input processing, not fixed stale storage guaranteed only to fault immediately.
* Controlled reclaim, replacement contents, arbitrary write, disclosure, and LPE are not shown. No separate C/I or extra availability point is awarded.
* Structured stale-object leverage is not separately scored: report operations through the stale object are grounded, but useful post-reuse behavior and attacker control of reclaimed storage are not.

3. Reachability analysis

The report source is an active Alps I2C HID device or its firmware. The complete adversarial trigger is unresolved: the evidence does not establish who can force registration failure, whether local memory pressure suffices, or whether a malicious device can reliably arrange the full sequence. No namespace capability is involved. Host-admin or UID-0 requirements are therefore unknown rather than assumed.

4. Primitive and severity reading

This is a runtime UAF of an active structured `input_dev`, not a cleanup-only dereference or repeated-release bug. The shown effect is stale input reporting with plausible host crash. A useful stale-object write or controlled reuse is unproven. Nevertheless, the device-influenced report is consumed by privileged host input processing through freed structured state, leaving material exploit leverage unresolved; therefore it remains a Class B Important candidate and is unsafe to auto-downgrade.

5. One-sentence report phrase

A registration-failure race leaves a freed input device reachable from active HID report processing, causing a host-kernel UAF with unresolved post-free input-state effects.

6. Manual review advice

MANUAL CHECK REQUIRED

Confirm full trigger control, exact input-reporting operations after the stale dereference, allocator reuse opportunities, and malicious-device versus local-user reachability.

7. Call-site confidence

Call-site confidence: medium

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

Patch: HID: alps: fix use-after-free on input2 registration failure
Commit: 64f824dccfd316fd3db8ea1cc4e8a76ad6a02740
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=64f824dccfd316fd3db8ea1cc4e8a76ad6a02740

Commit description:

alps_input_configured() stores data->input2 before calling
input_register_device().  If registration fails, input_free_device()
frees the input device but data->input2 still points to the freed memory.
alps_input_configured() calls hid_hw_open() before allocating input2, so
URBs are already active and raw_event can fire during the failure window.
A U1_SP_ABSOLUTE_REPORT_ID report arriving then causes u1_raw_event()
to dereference the freed data->input2 -> use-after-free.

Fix by only storing input2 into drvdata after successful registration
and adding a NULL guard in the raw_event path.

Fixes: 2562756 ("HID: add Alps I2C HID Touchpad-Stick support")
Cc: stable@vger.kernel.org
Signed-off-by: Chen Changcheng <chenchangcheng@kylinos.cn>
Signed-off-by: Jiri Kosina <jkosina@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/hid/hid-alps.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=64f824dccfd316fd3db8ea1cc4e8a76ad6a02740

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

The original Linux kernel CVE announcement for CVE-2026-98501 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98501

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:P/AC:H/PR:N/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: 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).