CVE-2026-64364

What the bug is

mt_io_flags is a single unsigned long, but mt_process_slot(), mt_release_pending_palms() and mt_release_contacts() use it as a per-slot bitmap indexed by the slot number. That slot number is only bounded by td->maxcontacts, which is taken from the device's ContactCountMaximum feature report and can be up to 255, not by BITS_PER_LONG. As a result, a multitouch device that advertises a large contact count makes set_bit()/clear_bit() operate past the mt_io_flags word and corrupt the adjacent members of struct mt_device. The sticky-fingers release timer is the easiest way to reach this. mt_release_contacts() runs for (i = 0; i < mt->num_slots; i++) clear_bit(i, &td->mt_io_flags); with num_slots == maxcontacts. For maxcontacts around 250 the loop clears the bits that overlap td->applications.next, zeroing that list head, and the list_for_each_entry() that immediately follows then dereferences NULL. The kernel panics from timer (softirq) context. On a KASAN build this shows up as a general protection fault in mt_release_contacts() with a null-ptr-deref at offset 0x58, which is offsetof(struct mt_application, num_received). The state is reachable from an untrusted USB or Bluetooth HID multitouch device; no local privileges are required. Store the per-slot active state in a separately allocated bitmap sized for maxcontacts, the same pattern already used for pending_palm_slots, and keep only MT_IO_FLAGS_RUNNING in mt_io_flags. The two "mt_io_flags & MT_IO_SLOTS_MASK" arming checks become bitmap_empty(td->active_slots, td->maxcontacts). Move MT_IO_FLAGS_RUNNING back to bit 0. It was bumped to bit 32 by the same commit to leave the low byte for the slot bits; with the slot bits gone it fits in bit 0 again, which also keeps it within the unsigned long on 32-bit.

Where it lives

The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.

drivers/hid/hid-multitouch.c

What this is

HID CORE LAYERMAINTAINERS section matched on drivers/hid/ · linux-input@vger.kernel.org · Maintained

Kernel module

hid_multitouch

Check it on the machine

grep -wE 'CONFIG_HID|CONFIG_HID_MULTITOUCH|CONFIG_HID_SUPPORT' /boot/config-$(uname -r)

Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.

lsmod | grep -w hid_multitouch

Prints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.

Show whether Debian builds this, per release

Debian builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.

• bookworm, trixieMnot built on arm64/cloud-arm64
• forky, sidMnot built on amd64/cloud-amd64, arm64/cloud-arm64
• bookworm · linux-6.12Mnot built on arm64/cloud-arm64

M

a module where it is built at all; some flavours do not build it

Build switches

CONFIG_HID, CONFIG_HID_MULTITOUCH, CONFIG_HID_SUPPORT

Reads as

all on means the file is compiled; any one off means it is not.

From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages

Signals

Published

2026-07-25 (3 months ago)source

CVSS

8.8 high
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsource recompute it

Attack vector

adjacent network (AV:A)source

EPSS

0.35%, higher than 27.6% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

not yet assignedsource

Subsystem

drivers/hid

Upstream fixes

The versions the CNA records as introducing and fixing this, and the commit for each. source

Introduced	Fixed in	Commit
5.10.246	5.10.261	12e90656e330
5.15.196	5.15.212	152983d87387
6.1.158	6.1.178	b5c037d6b807
6.6.114	6.6.145	a6d5ce2e1a2d
6.12.55	6.12.97	e24918ee67c4
6.18	6.18.39	37daa8c96bd5
6.18	7.1.4	6493ebf9489e
6.18	7.2	8813b0612275
6.17.5	0	0

Debian advisories