# CVE-2026-80660: hwmon: (occ) unregister sysfs devices outside occ lock

> A race condition in the Linux kernel OCC driver can cause a deadlock, leading to a local denial of service.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 28 Aug 2026
- **Updated:** 28 Aug 2026
- **Also known as:** BELL-CVE-2026-80660, DEBIAN-CVE-2026-80660, GHSA-4rpr-p877-fc2p, UBUNTU-CVE-2026-80660

## What is CVE-2026-80660?

CVE-2026-80660 is a vulnerability in Linux, published on 28 Aug 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:

hwmon: (occ) unregister sysfs devices outside occ lock

occ_active(false) and occ_shutdown() unregister sysfs-backed devices while
occ->lock is held.  hwmon_device_unregister() and sysfs_remove_group() can
wait for active sysfs callbacks to drain, and those callbacks can enter the
OCC update path and try to take occ->lock again.  That gives the unregister
paths the lock ordering occ->lock -> sysfs callback drain, while a callback
has the opposite edge sysfs callback -> occ->lock.

This issue was found by our static analysis tool and then manually
reviewed against the current tree.

The grounded PoC kept the real unregister and callback carrier:

  occ_shutdown()
  hwmon_device_unregister()
  occ_show_temp_1()
  occ_update_response()

Lockdep reported the circular dependency with occ_shutdown() already
holding the OCC mutex and hwmon_device_unregister() waiting on the sysfs
side:

  WARNING: possible circular locking dependency detected
  ... (sysfs_lock) ... at: hwmon_device_unregister+0x12/0x30 [vuln_msv]
  ... (&test_occ.lock) ... at: occ_shutdown.constprop.0+0xe/0x40 [vuln_msv]
  occ_update_response.isra.0+0xb/0x20 [vuln_msv]
  occ_show_temp_1.constprop.0.isra.0+0x23/0x40 [vuln_msv]
  *** DEADLOCK ***

Serialize hwmon registration and removal with a separate hwmon_lock.
Under that lock, detach occ->hwmon and update occ->active while occ->lock
is held so concurrent OCC state changes still see a stable state, then
drop occ->lock before calling hwmon_device_unregister().  Remove the
driver sysfs group before taking occ->lock in occ_shutdown(), so draining
the driver attributes cannot wait while the OCC mutex is held.  Also make
OCC update callbacks return -ENODEV after deactivation, so callbacks that
already passed sysfs active protection do not poll the hardware after
teardown has detached the hwmon device.

## Which versions are affected by CVE-2026-80660?


## How do I fix CVE-2026-80660?

Apply the vendor's patch.

## Is CVE-2026-80660 being exploited?

There is no known exploitation of CVE-2026-80660 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80660 and fix it if it is affected.

What it is: CVE-2026-80660 is a vulnerability in Linux, published on 28 Aug 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-2026-80660 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-2026-80660/ (Markdown: https://insights.sbomify.com/CVE-2026-80660/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80660
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80660
- OSV: https://osv.dev/vulnerability/CVE-2026-80660

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80660/
Summaries are generated and may contain mistakes; the official description above is the record.