[CVE-2026-80781][MODERATE REGULAR] HID: core: fix OOB read of field->usage in hid_set_field()

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

CVE: CVE-2026-80781
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: HID: core: fix OOB read of field->usage in hid_set_field()
Commit: 465544b3d6602cfbdc2305d5cbfb7f4954353b63
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=465544b3d6602cfbdc2305d5cbfb7f4954353b63
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80781
Analysis date: Fri, 04 Sep 2026 17:16:22 -0400
ActionableScore: 3
ActionableScore lower bound: 2
Actionable bucket: Borderline / manual review recommended
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-80781 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80781

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: YES

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

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

CVE-2026-80781	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-80781 CHECK WITH IMPACT FROM ORIG NN MODERATE	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:N/A:H';CWE-125;*CWE-20;CWE-129;Other CVSS 'AV:P/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L';BEST CVSS score: '5.3';DESCR 'An OOB read in the HID core path occurs because hid_set_field calls hid_dump_input before checking whether offset is within field report_count. Under CONFIG_DEBUG_FS, hid_dump_input can dereference field usage plus an out of range offset and read past the usage array when a malformed or unusual HID report layout is present. A known trigger path is picolcd framebuffer deferred IO, where fixed offsets can be passed to hid_set_field even when the bound field has fewer usages. For the CVSS the PR:L is used in the paranoid score because a local user or process may be able to trigger the framebuffer or HID dependent path after such a device is present. The issue is not network reachable and typically requires a local or physical HID device context. Impact is mainly denial of service and a limited kernel OOB read. YES REQUIRES MANUAL CHECK.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3)  SKIP CVE-2026-80781 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES  NO NO unknown 	MAYBE	READ KASAN OOB USB HARDWARE LINUS  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH	-	-	checked

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

ActionableScore=3
ActionableScoreLower=2
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 2
* Conservative score: 2
* Raw paranoid score: 3
* Paranoid score: 3
* Applied conservative floor/cap: none
* Applied paranoid floor/cap: none
* Final recommended bucket: **Borderline / manual review recommended**::

2. Signal breakdown

Positive signals:

* +1 Limited read-only OOB primitive. `hid_set_field()` passed `field->usage + offset` to `hid_dump_input()` before validating `offset`, and `hid_dump_input()` can dereference `usage->hid` under `CONFIG_DEBUG_FS`.
* +1 Attacker-influenced malformed or unusual HID device context. The report layout can have fewer usages than the fixed offsets used by the visible `picolcd_fb_send_tile()` caller, making the invalid offset concrete rather than purely theoretical.
* Paranoid only +1 Plausible DoS or fault concern. KASAN reports a 4-byte slab-out-of-bounds read, and the framebuffer deferred-io path can repeatedly drive the bad read on each tile.

Negative or non-awarded signals:

* 0 Real UAF not awarded. No object lifetime violation, stale freed pointer, or post-free access is established.
* 0 Concrete repeated release/refcount not awarded. There is no first release, surviving dangling reference, or second lifetime mutation.
* 0 Controlled reclaim not demonstrated.
* 0 Arbitrary or directed kernel write not demonstrated.
* 0 Confidentiality not awarded. The OOB value is read internally by HID debug formatting, but no userspace, network, or device-visible disclosure path is established.
* 0 Integrity not awarded. The patch fixes pointer validation before a read, not a write or policy mutation.
* 0 Remote reachability not established. This is HID/device/local path behavior, not network packet processing.
* 0 Strong LPE or structured stale-object leverage not awarded. The primitive is a limited OOB read, not active-object reuse or controllable corruption.
* 0 Extra availability not awarded for the same KASAN/OOB symptom beyond the paranoid DoS point.

3. Reachability analysis

The most direct attacker model is a malformed or unusual HID device that registers a field with fewer usages than expected by a caller such as `picolcd_fb_send_tile()`. The supplied context also shows a local framebuffer deferred-io path that can repeatedly call `hid_set_field()` with fixed offsets 11..42 after such a device is present.

Host administrator privilege is not positively required for the bug mechanics, because a physical or device-side attacker can influence HID descriptors/report layout without host root. However, practical reachability depends on the affected HID driver path, `CONFIG_DEBUG_FS`, and availability of the specific framebuffer/HID interaction. No namespace-scoped privilege is involved.

No network reachability is established. No race is involved. No prior host-admin setup is clearly required by the primitive itself, although the affected device/path is specialized.

4. Primitive and severity interpretation

The exact primitive is a bounded read past the end of the `field->usage` array caused by performing pointer arithmetic and dereference before the `offset >= field->report_count` guard. The patch-supported primitive is read-only OOB access of `usage->hid`.

This is not active structured UAF and not fixed stale storage. It is not cleanup/destructor lifetime behavior. No concrete repeated release/refcount operation exists. No first lifetime operation can free an object, and no second operation mutates lifetime/refcount state.

PrimitiveClass is CLASS_C because the demonstrated behavior is a limited invalid kernel read with possible crash/DoS behavior, but without an independently useful corruption, disclosure, write, boundary-bypass, or LPE primitive.

ImportantCandidate is NO because the supplied evidence does not establish memory corruption beyond read-only OOB, controlled reclaim, arbitrary write, information disclosure, or privilege escalation. ManualReview is RECOMMENDED because it is still a real kernel memory-safety bug with a concrete call site and device-controlled input. AutoDowngradeAllowed is YES because the established primitive is constrained and does not leave unresolved Important-grade exploitation leverage.

Likely operational severity is ordinary Moderate to borderline actionable Moderate depending on whether the affected HID/picolcd/debugfs path is present and reachable.

5. One-sentence report phrase

A HID core OOB read occurs because hid_set_field() calls hid_dump_input() before validating offset, allowing a malformed or unusual HID report layout to make field->usage plus offset point outside the usage array and potentially cause a limited kernel OOB read or DoS under CONFIG_DEBUG_FS.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: the issue has a concrete OOB read primitive and visible caller path, but no demonstrated disclosure, write, UAF, privilege escalation, or network reachability.

7. Call-site confidence

Call-site confidence: high

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

Patch: HID: core: fix OOB read of field->usage in hid_set_field()
Commit: 465544b3d6602cfbdc2305d5cbfb7f4954353b63
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=465544b3d6602cfbdc2305d5cbfb7f4954353b63

Commit description:

hid_set_field() hands field->usage + offset to hid_dump_input() before
the guard that bounds offset:

	hid_dump_input(field->report->device, field->usage + offset, value);

	if (offset >= field->report_count) {
		hid_err(...);
		return -1;
	}

Under CONFIG_DEBUG_FS hid_dump_input() dereferences that pointer, with
buf = hid_resolv_usage(usage->hid, NULL).  The usage[] array is
allocated inline with the hid_field in hid_register_field() and holds
field->maxusage entries, so an offset past it reads off the end of the
kvzalloc()ed allocation and into a neighbouring object.  Had the guard
run first, offset < report_count <= maxusage would already have confined
the pointer to the array.

A caller supplies such an offset today.  picolcd_fb_send_tile()
validates only report->maxfield before issuing
hid_set_field(report->field[0], 11 + i, ...) for i = 0..31, so its
offsets are fixed at 11..42 and are never checked against the bound
field.  When the device registers that field with fewer usages, the
framebuffer deferred-io work drives the read on every tile.  KASAN
reports a 4-byte slab-out-of-bounds read in hid_dump_input() below
hid_set_field(), and the same boot logs "offset (1) exceeds
report_count (1)" from the guard that runs only afterwards.

Move the hid_dump_input() call below the guard.  Because
field->maxusage >= field->report_count, the guard then establishes that
field->usage + offset lies inside the array before it is dereferenced,
for every caller and without changing behaviour on the valid path.

Discovered by XBOW, triaged by Baul Lee <baul.lee@xbow.com>

Fixes: 1da177e ("Linux-2.6.12-rc2")
Reported-by: Federico Kirschbaum <federico.kirschbaum@xbow.com>
Reported-by: Baul Lee <baul.lee@xbow.com>
Cc: stable@vger.kernel.org
Signed-off-by: Baul Lee <baul.lee@xbow.com>
Signed-off-by: Jiri Kosina <jkosina@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/hid/hid-core.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=465544b3d6602cfbdc2305d5cbfb7f4954353b63

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

The original Linux kernel CVE announcement for CVE-2026-80781 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80781

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:L/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:H
  The Best / paranoid CVSS score: 5.3

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: 2
  Paranoid ActionableScore: 3

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).