[CVE-2026-93189][MODERATE 7.0] HID: core: quiesce input in hid_hw_stop() to prevent use-after-free [ Upstream

[CVE-2026-93189][MODERATE 7.0] HID: core: quiesce input in hid_hw_stop() to prevent use-after-free [ Upstream

[AL-KERNEL]

CVE: CVE-2026-93189
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: HID: core: quiesce input in hid_hw_stop() to prevent use-after-free [ Upstream
Commit: 0744cb9520aade37e78f69134f3111086158f1d2
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0744cb9520aade37e78f69134f3111086158f1d2
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93189
Analysis date: Thu, 17 Sep 2026 17:18:00 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
A race in the HID core stop path can allow in-flight HID reports to reach `hidraw_report_event()` after `hid_disconnect()` has freed the backing hidraw object, causing a real kernel use-after-free and at least local or device-mediated denial of service.

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

The original Linux kernel CVE announcement for CVE-2026-93189 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93189

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
======================================================================

CVE-2026-93189	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-93189 CHECK WITH IMPACT FROM ORIG NN LOW	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-667;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A race in the HID core stop path can allow in-flight HID reports to reach hidraw_report_event after hid_disconnect has freed the backing hidraw object. This is a use-after-free condition and can at least crash the kernel when a probe path fails after hid_device_io_start but before input delivery is explicitly stopped. For the CVSS the PR:L is used for the paranoid score because reliable triggering generally requires local code execution, local device control, or access to a controllable HID emulation path rather than a pure unauthenticated network request. The issue is not directly network reachable and normally depends on local HID device activity, USB or similar local attachment, driver probe failure, and timing of report delivery. Impact is at least local denial of service via kernel crash and in worst case may allow confidentiality or integrity impact due to kernel use-after-free memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5)	YES	DANGER USB INIT ERRORPATH UAF HARDWARE LINUS SYZBOT KPANIC PACKET 	NO	NO	checked

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

ActionableScore=5
ActionableScoreLower=4
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO

## 1. ActionableScore

* Raw conservative score: 4
* Conservative score: 4
* Raw paranoid score: 5
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

No floor or cap changed the conservative score. No floor or cap changed the paranoid score.

## 2. Signal breakdown

Conservative signals:

* +2 Real UAF / active lifetime violation. The commit directly states that `hid_disconnect()` may free `struct hidraw` while in-flight HID reports on another CPU still dereference it through `hidraw_report_event()`.
* +1 Reliable kernel crash / strong DoS. syzbot reports the resulting use-after-free, and this path can plausibly produce KASAN reports, Oops, or kernel crash.
* +1 Firmware/device-mediated external influence. The stale use is driven by HID report delivery from a device path rather than by a pure local syscall or unauthenticated network packet.

Paranoid additional signal:

* +1 Broad active input-path exposure. The fix is centralized in HID core and the commit identifies multiple affected callers across several HID/HWMON drivers, so this is not a single isolated per-driver mistake.

Important non-awarded signals:

* Controlled reclaim not demonstrated.
* Arbitrary write not demonstrated.
* Direct remote network reachability not established.
* Structured stale-object exploitation leverage not awarded because the evidence does not show attacker-controlled replacement object fields being consumed after reuse.
* Weak LPE not separately awarded solely because this is a UAF.
* Extra Availability not awarded because the same crash is already counted once.
* C/I not awarded in ActionableScore merely because UAF could theoretically affect reclaimed memory.
* Concrete repeated release/refcount signal not awarded.

Repeated-release/refcount check:

* First release can end lifetime: yes, `hid_disconnect()` can free the `hidraw` backing object.
* Exact same reference survives: yes, in-flight HID report handling may still hold or reach the stale object path.
* Second operation is a real lifetime/refcount mutation: no, the described stale operation is dereference/use in `hidraw_report_event()`, not a second `put`, `release`, `kfree`, or refcount mutation.
* +1 Concrete repeated release/refcount awarded: no.
* Paranoid repeated-refcount leverage +1 awarded: no.
* FLOOR 5 applied: no. The final paranoid score reaches 5 by signal arithmetic, not by repeated-release floor.

## 3. Reachability analysis

The likely trigger involves a HID device or HID emulation path where input delivery has been started by `hid_device_io_start()`, then the driver probe fails later and unwinds through `hid_hw_stop()` without first stopping input. A malicious or controllable local HID device could plausibly influence report timing and contents, but the supplied evidence does not fully establish a complete ordinary local unprivileged software-only trigger.

Host-admin-equivalent privilege is not positively established, but below-host-admin reachability for the complete trigger is also not fully proven from the supplied patch alone. Therefore `HostAdminRequired=UNKNOWN`.

No namespace-scoped privilege path is involved or established. This is not a network namespace or container capability issue.

Prior host setup may include the affected HID driver being present and a matching device or emulated device being attached. The bug is not directly network reachable. The race is timing-dependent because an in-flight report must overlap with probe unwind and disconnect, but the evidence does not prove a rare or externally uncontrollable one-shot race, so no timing penalty is applied.

## 4. Primitive and severity interpretation

The exact primitive is a real kernel use-after-free: `hid_disconnect()` may free hidraw state while concurrent HID report processing still reaches `hidraw_report_event()` and dereferences the freed backing object.

This is an active structured-object UAF rather than a pure fixed stale DMA buffer. However, the demonstrated stale use is still limited to in-flight report handling during probe failure/unwind, and the patch does not show controlled reclaim, replacement-object shaping, arbitrary read/write, callback hijack, or credential/security-object modification.

This is `CLASS_B`: a real kernel lifetime primitive whose exploitation leverage is unresolved. It is not `CLASS_A` because no strong exploitation primitive is demonstrated. It is not `CLASS_C` because a real UAF is directly established, not merely a WARN, NULL dereference, or passive invalid state.

Demonstrated consequence is local or device-mediated kernel crash/DoS. Speculative consequence is possible confidentiality or integrity impact if reclaimed memory could be meaningfully shaped and consumed by the stale report path, but that is not proven by the supplied evidence.

`ImportantCandidate=YES` because this is an active HID input-path UAF with multiple affected callers and unresolved exploitation leverage beyond a simple NULL dereference. `AutoDowngradeAllowed=NO` because automatically closing this as ordinary Moderate would discard a concrete kernel lifetime-corruption primitive that still requires manual exploitability review.

Likely operational severity is Actionable Moderate, with Strong Important candidacy depending on whether further analysis demonstrates controllable reclaim, attacker-shaped replacement, or a reliable below-host-admin trigger.

## 5. One-sentence report phrase

A race in the HID core stop path can allow in-flight HID reports to reach `hidraw_report_event()` after `hid_disconnect()` has freed the backing hidraw object, causing a real kernel use-after-free and at least local or device-mediated denial of service.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is a real active-object UAF in a kernel input path with multiple affected drivers, and the available evidence does not fully resolve exploitability, attacker reachability, or whether practical impact is limited to crash-only DoS.

## 7. Call-site confidence

Call-site confidence: high

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

Patch: HID: core: quiesce input in hid_hw_stop() to prevent use-after-free [ Upstream
Commit: 0744cb9520aade37e78f69134f3111086158f1d2
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0744cb9520aade37e78f69134f3111086158f1d2

Changed files:
  drivers/hwmon/corsair-cpro.c
  drivers/hwmon/nzxt-kraken3.c
  drivers/hwmon/nzxt-smart2.c
  drivers/hwmon/gigabyte_waterforce.c
  drivers/hid/hid-logitech-dj.c
  drivers/hid/hid-nintendo.c
  drivers/hid/hid-mcp2221.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=0744cb9520aade37e78f69134f3111086158f1d2

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

The original Linux kernel CVE announcement for CVE-2026-93189 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93189

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).