[CVE-2026-80780][IMPORTANT] HID: pidff: fix OOB write when hid->inputs is empty [ Upstream

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

CVE: CVE-2026-80780
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: HID: pidff: fix OOB write when hid->inputs is empty [ Upstream
Commit: 2e0471bf3ab2a6b7eedcc3b8a2a17286b6a9ae1a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2e0471bf3ab2a6b7eedcc3b8a2a17286b6a9ae1a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80780
Analysis date: Fri, 04 Sep 2026 17:51:12 -0400
ActionableScore: 6
ActionableScore lower bound: 5
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
A malicious USB HID device can trigger a type-confusion OOB write in the HID pidff force-feedback probe path when `hid->inputs` is empty, causing kernel memory corruption and likely DoS, with stronger exploitation requiring manual review.

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

The original Linux kernel CVE announcement for CVE-2026-80780 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80780

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: IMPORTANT
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-2026-80780	IMPORTANT	https://www.kernelcve.org/list/?q=CVE-2026-80780 CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H';*CWE-787;CWE-843;*CWE-20;Other CVSS 'AV:P/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '6.8';DESCR 'An OOB write in the HID pidff force-feedback initialization path can occur when hid_pidff_init_with_quirks() is called with an empty hid inputs list. The code derives a hid_input from the empty list head, treats unrelated hid_device memory as an input_dev, and then writes through the type-confused pointer during force-feedback setup. A malicious USB HID device with a PID usage page can reach this path during the hotplug probe flow without attacker software running on the victim. For the CVSS the PR:N value is used because no local account or victim-side privileges are required once the device can be attached. The issue is not network reachable and requires physical device insertion or an equivalent trusted peripheral path. Impact is at least denial of service via kernel memory corruption, and in the paranoid interpretation may include confidentiality and integrity impact because the primitive includes OOB writes and writes of pointer values in kernel memory.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 6)  SKIP CVE-2026-80780 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES  NO NO unknown 	MAYBE	WRITE KASAN OOB USB HARDWARE LINUS KPANIC 	-	-	checked

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

ActionableScore=6
ActionableScoreLower=5
PrimitiveClass=CLASS_A
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO

## 1. ActionableScore

* Raw conservative score: 4
* Conservative score: 5
* Applied conservative floor/cap: 4 -> 5 because a concrete kernel OOB write / type-confusion primitive is established and is reachable without host-admin privilege once a malicious USB HID device is attached.
* Raw paranoid score: 6
* Paranoid score: 6
* Applied paranoid floor/cap: none
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

## 2. Signal breakdown

Positive signals:

* +2 Strong corruption primitive: the patch establishes a real OOB write through a type-confused `input_dev` pointer derived from an empty `hid->inputs` list.
* +2 Strong exploitation leverage: the corrupted path writes through `dev->ffbit`, and `input_ff_create()` can add further writes of a heap pointer and function pointers. This is more than a simple NULL dereference or crash-only invalid read.
* +1 Firmware/peripheral-mediated external influence: a malicious USB HID device can provide the descriptor that reaches the vulnerable probe path.
* +1 Reliable kernel crash / strong DoS: KASAN reports an 8-byte OOB write in the hotplug workqueue, and kernel memory corruption can realistically crash the host.
* +1 Paranoid-only integrity concern: the primitive performs concrete writes to kernel memory outside the intended object. This is not treated as arbitrary write, but it is enough to preserve manual-review sensitivity.
* +1 Paranoid-only broad exposure concern: USB HID hotplug and automatic driver probing are common attack surfaces, although the vulnerable PID force-feedback path is more specific than generic HID.

Negative signals:

* -2 Physical/peripheral access requirement: the supplied trigger is plugging in a malicious USB HID device or an equivalent trusted peripheral path. No network reachability is established.

Important non-awarded signals:

* RealUAF not awarded: this is not a lifetime or stale-object use-after-free. It is OOB write / type confusion.
* Controlled reclaim not demonstrated.
* Arbitrary kernel read/write not demonstrated.
* Confidentiality impact not awarded because no disclosure path is shown.
* Remote network reachability not established.
* Extra availability point not awarded because the crash/DoS effect is already counted once.
* Repeated release/refcount signal not applicable.
* Namespace-scoped privilege not applicable.

## 3. Reachability analysis

The evaluated attacker is a physical or peripheral attacker able to attach a malicious USB HID device. The commit states that no attacker software and no logged-in user are required on the victim once the device is plugged in.

Host-admin privilege is not required for the vulnerable kernel path itself. The bug is reached during USB HID probe on the hotplug workqueue. The attacker supplies a HID report descriptor with a PID usage page while leaving `hid->inputs` empty, allowing `universal_pidff_probe()` to call `hid_pidff_init_with_quirks()` without the previous `HID_CLAIMED_INPUT` guarantee.

This is not network reachable. It requires physical device insertion or an equivalent trusted peripheral/USB redirection path. No namespace or CAP-based trigger is relevant. No hard race is involved. The trigger is deterministic once the crafted descriptor reaches the affected probe path.

## 4. Primitive and severity interpretation

The exact primitive is a type confusion leading to OOB writes. `hid_pidff_init_with_quirks()` used `list_entry(hid->inputs.next, struct hid_input, list)` without checking whether the list was empty. For an empty list, the computed `hid_input` aliases unrelated `hid_device` memory. The subsequent `hidinput->input` load produces a type-confused `input_dev` pointer, and force-feedback initialization writes through that invalid object interpretation.

This is not an ordinary cleanup crash, not a UAF, and not a mere validation-only bug. It is an active kernel memory corruption primitive in a device probe path. The demonstrated consequence is an OOB write and likely host DoS. The speculative consequence is stronger exploitation from kernel memory corruption, especially because the path includes writes of pointer values, but no controlled target selection, controlled reclaim, arbitrary write, or public LPE chain is supplied.

PrimitiveClass is CLASS_A because a concrete OOB write / type-confusion primitive is directly established. ImportantCandidate is YES because the bug is a real kernel memory corruption issue reachable without victim-side privileges beyond device attachment. AutoDowngradeAllowed is NO because automatically treating this as ordinary Moderate would discard a concrete kernel corruption primitive with unresolved exploitation leverage.

Likely operational severity is actionable Moderate at minimum, with Strong Important review justified despite the physical/peripheral attack vector.

## 5. One-sentence report phrase

A malicious USB HID device can trigger a type-confusion OOB write in the HID pidff force-feedback probe path when `hid->inputs` is empty, causing kernel memory corruption and likely DoS, with stronger exploitation requiring manual review.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: concrete kernel OOB writes and type confusion are established, including writes of pointer-like values, and the issue is reachable through malicious peripheral input without host-admin privileges.

## 7. Call-site confidence

Call-site confidence: high

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

Patch: HID: pidff: fix OOB write when hid->inputs is empty [ Upstream
Commit: 2e0471bf3ab2a6b7eedcc3b8a2a17286b6a9ae1a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2e0471bf3ab2a6b7eedcc3b8a2a17286b6a9ae1a

Changed files:
  drivers/hid/usbhid/hid-pidff.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=2e0471bf3ab2a6b7eedcc3b8a2a17286b6a9ae1a

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

The original Linux kernel CVE announcement for CVE-2026-80780 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80780

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:L/PR:N/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 6.8

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: 5
  Paranoid ActionableScore: 6

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: IMPORTANT
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): IMPORTANT

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).