CVE-2026-98859 HID: multitouch: stop the release timer from being rearmed on remove
A use-after-free vulnerability in the Linux kernel HID multitouch driver allows local attackers to cause a system crash or potentially execute code via a race condition during device removal.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-98859?
CVE-2026-98859 is an use after free vulnerability in Linux, published on 18 Oct 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: multitouch: stop the release timer from being rearmed on remove
mt_remove() quiesces the sticky-finger timer before stopping the hardware:
timer_delete_sync(&td->release_timer);
sysfs_remove_group(&hdev->dev.kobj, &mt_attribute_group); hid_hw_stop(hdev);
timer_delete_sync() waits for a running callback and dequeues the timer, but it does not stop the timer from being armed again. The transport is still delivering reports at that point, and the report path rearms it:
if (app->quirks & MT_QUIRK_STICKY_FINGERS) { if (td->mt_io_flags & MT_IO_SLOTS_MASK) mod_timer(&td->release_timer, jiffies + msecs_to_jiffies(100));
A report that arrives after timer_delete_sync() has returned therefore leaves the timer queued. td is allocated with devm_kzalloc() against hdev->dev, so it is freed when the driver is unbound, after mt_remove() returns. When the timer fires afterwards, mt_expired_timeout() dereferences the freed td:
struct mt_device *td = timer_container_of(td, t, release_timer); struct hid_device *hdev = td->hdev;
if (test_and_set_bit_lock(MT_IO_FLAGS_RUNNING, &td->mt_io_flags))
Simply moving the teardown after hid_hw_stop() does not fix this on its own, because mt_expired_timeout() calls mt_release_contacts(), which walks hdev->inputs; the timer still has to be quiesced before hid_hw_stop() tears the input devices down.
Use timer_shutdown_sync() instead, which additionally makes any later mod_timer() a no-op, so neither ordering constraint has to be traded off against the other. This is the final-teardown pattern the function was introduced for, and hid-wiimote already uses it for the same reason.
Which versions are affected by CVE-2026-98859?
How do I fix CVE-2026-98859?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-98859 being exploited?
There is no known exploitation of CVE-2026-98859 in the wild and no public exploit code.
Sources
Also known as AZL-108818, BELL-CVE-2026-98859, DEBIAN-CVE-2026-98859, GHSA-rf84-p87x-87h6, UBUNTU-CVE-2026-98859.