# CVE-2026-80781: HID: core: fix OOB read of field->usage in hid_set_field()

> An out-of-bounds read in the Linux kernel HID subsystem allows local attackers to leak memory or crash the system when debugfs is enabled.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 4 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-99407, BELL-CVE-2026-80781, DEBIAN-CVE-2026-80781, GHSA-4wjj-fc9c-xhfj, UBUNTU-CVE-2026-80781

## What is CVE-2026-80781?

CVE-2026-80781 is a memory corruption vulnerability in Linux, published on 4 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

HID: core: fix OOB read of field->usage in hid_set_field()

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>

## Which versions are affected by CVE-2026-80781?


## How do I fix CVE-2026-80781?

Apply the vendor's patch.

## Is CVE-2026-80781 being exploited?

There is no known exploitation of CVE-2026-80781 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80781 and fix it if it is affected.

What it is: CVE-2026-80781 is a memory corruption vulnerability in Linux, published on 4 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-80781 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-80781/ (Markdown: https://insights.sbomify.com/CVE-2026-80781/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80781
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80781
- OSV: https://osv.dev/vulnerability/CVE-2026-80781

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80781/
Summaries are generated and may contain mistakes; the official description above is the record.