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.
- 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
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.
Sources
Also known as BELL-CVE-2026-80660, DEBIAN-CVE-2026-80660, GHSA-4rpr-p877-fc2p, UBUNTU-CVE-2026-80660.