[CVE-2026-64277][IMPORTANT] Input: synaptics-rmi4 - bound the F3A keymap to the GPIO count

[AL-KERNEL <alkernel@kernelcve.org>]

CVE: CVE-2026-64277
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: Input: synaptics-rmi4 - bound the F3A keymap to the GPIO count
Commit: 502ad7caaa1a445b734c827fa256e5311df67e3d
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=502ad7caaa1a445b734c827fa256e5311df67e3d
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64277
Analysis date: Sat, 25 Jul 2026 08:59:51 -0400
ActionableScore: 7
ActionableScore lower bound: 6
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
An undersized Synaptics RMI4 F3A keymap allocation can expose OOB read via EVIOCGKEYCODE and caller-controlled OOB write via EVIOCSKEYCODE to a local process with evdev access, creating information disclosure, kernel crash, and plausible local privilege escalation risk.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-64277 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64277

The original announcement does not normally provide a security severity
estimate, CVSS assessment, or enough information to determine whether the
reported kernel bug represents a practically relevant security issue.

This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin. It combines
an autonomous classifier with LLM-assisted technical analysis and a
separate ActionableScore mechanism.

The purpose of this report is to prioritize Linux kernel CVEs before
manual review, identify cases that require prompt investigation, and
support automatic closure of issues that are unlikely to have meaningful
security impact.

Published priority for this report: IMPORTANT
Manual review required: YES

A detailed explanation of the methodology and priority rules is included
at the end of this message.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-64277	IMPORTANT	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';CWE-131;CWE-125;*CWE-787;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'An undersized keymap allocation in the Synaptics RMI4 F3A input driver can make gpio_key_map smaller than the gpio_count later exposed through the input device. If an affected or malicious device reports more than 6 GPIOs, the driver may read past the keymap during attention handling and the input core keycode ioctls may access entries beyond the allocated buffer. A local process able to open the evdev node can use EVIOCGKEYCODE for an out of bounds read and EVIOCSKEYCODE for a caller controlled out of bounds write. For the CVSS the PR:L is used because exploitation requires local user or process access to the evdev interface, not remote network access. The issue is not network reachable. Impact is at least local denial of service or information disclosure, and in the worst case may allow privilege escalation due to kernel heap memory corruption. YES REQUIRES MANUAL CHECK';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7)	YES	OOB LEAK HARDWARE LINUS  KPANIC INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=7
ActionableScoreLower=6

## 1. ActionableScore

* Conservative score: 6
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Triggered signals:

* Firmware-mediated external influence: +1
  The vulnerable allocation size depends on `gpio_count` reported by the Synaptics RMI4 F3A device query register.

* Local unprivileged trigger: +1
  Any local process able to open the affected evdev node can potentially reach `EVIOCGKEYCODE` and `EVIOCSKEYCODE`.

* Privilege escalation plausible: +2
  The patch context describes a caller-controlled out-of-bounds write through `EVIOCSKEYCODE`, which is a plausible kernel heap corruption primitive.

* Generic memory corruption, strong corruption primitive: +2
  This is not only an invalid read. The undersized `gpio_key_map` can be accessed beyond allocation bounds, including a user-controlled write past the allocated buffer.

* Reliable kernel crash / strong DoS: +1
  OOB reads during attention handling and OOB writes through input ioctls can plausibly crash the kernel.

* Confidentiality impact plausible: +1
  `EVIOCGKEYCODE` can read past the allocated keymap and may disclose adjacent slab memory to userspace.

* Integrity impact plausible: +1
  `EVIOCSKEYCODE` can write a caller-controlled value beyond the allocated keymap.

Subtracting signals:

* Physical-only or rare hardware condition: -2
  Practical exposure depends on an affected Synaptics RMI4 F3A device, or a malicious or unusual device reporting `gpio_count > 6`.

* Corruption primitive constrained by layout and target uncertainty: -1 in conservative score only
  The OOB write is real, but practical exploitation depends on slab adjacency, object placement, evdev permissions, and the exact size/value written.

Paranoid score removes the constrained-primitive subtraction because a local OOB read plus caller-controlled OOB write in a kernel heap object should not be auto-closed without manual review.

## 3. Reachability analysis

The issue is locally reachable through the input subsystem when the affected RMI4 F3A device is present and exposes an evdev node. A local user or process with permission to open that evdev node may trigger the keycode ioctl paths. The device-side precondition is important: the device must report more than 6 GPIOs, while the old allocation used only `min(gpio_count, TRACKSTICK_RANGE_END)`.

This is not network reachable. Containers and namespaces may matter if the evdev node is passed into a container or exposed to a less trusted service. In normal desktop or laptop deployments, evdev access may be restricted by seat/session permissions, but it is not equivalent to full root or CAP_SYS_ADMIN.

Call-site confidence: high for the described ioctl and attention paths because the commit message explicitly identifies `rmi_f3a_attention()`, `input->keycodemax`, `input->keycode`, `EVIOCGKEYCODE`, and `EVIOCSKEYCODE`.

## 4. Severity interpretation

This is stronger than an ordinary Moderate issue because the bug provides both an OOB read and a caller-controlled OOB write from a local userspace-accessible input interface. The realistic exploitation conditions are hardware-dependent and likely not broadly exposed on servers, which keeps the conservative score below clear High/Critical territory.

Theoretical memory corruption potential is significant due to kernel heap OOB write. Realistic privilege escalation is plausible but not demonstrated from the patch alone, so this fits best as an Actionable Moderate at minimum and a Strong Important candidate for manual review.

## 5. One-sentence report phrase

An undersized Synaptics RMI4 F3A keymap allocation can expose OOB read via EVIOCGKEYCODE and caller-controlled OOB write via EVIOCSKEYCODE to a local process with evdev access, creating information disclosure, kernel crash, and plausible local privilege escalation risk.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is a concrete kernel heap OOB read/write primitive reachable from a local input device interface, with plausible confidentiality, integrity, availability, and LPE implications despite hardware-dependent exposure.

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UPSTREAM PATCH SUMMARY
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Patch: Input: synaptics-rmi4 - bound the F3A keymap to the GPIO count
Commit: 502ad7caaa1a445b734c827fa256e5311df67e3d
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=502ad7caaa1a445b734c827fa256e5311df67e3d

Commit description:

rmi_f3a_initialize() takes the GPIO count from the device query register
(f3a->gpio_count = buf & RMI_F3A_GPIO_COUNT, range 0..127).
rmi_f3a_map_gpios() then allocates gpio_key_map with
min(gpio_count, TRACKSTICK_RANGE_END) == at most 6 entries, but
rmi_f3a_attention() iterates the full gpio_count and dereferences
gpio_key_map[i], and input->keycodemax is set to the full gpio_count
while input->keycode points at the 6-entry allocation.

A device that reports gpio_count > 6 therefore causes an out-of-bounds
read of gpio_key_map[] on every attention interrupt, and out-of-bounds
accesses through the input core's default keymap ioctls: EVIOCGKEYCODE
reads past the buffer (leaking adjacent slab memory to user space) and
EVIOCSKEYCODE writes a caller-controlled value past it, for any process
able to open the evdev node, since input_default_getkeycode() and
input_default_setkeycode() only bound the index against keycodemax.

Size the keymap for the full gpio_count. The mapping loop is unchanged:
it still assigns only the first min(gpio_count, TRACKSTICK_RANGE_END)
entries; the remaining slots stay KEY_RESERVED (devm_kcalloc zero-fills)
and are skipped when reporting.

Fixes: 9e4c596 ("Input: synaptics-rmi4 - add support for F3A")
Cc: stable@vger.kernel.org
Signed-off-by: Bryam Vargas <hexlabsecurity@proton.me>
Link: https://patch.msgid.link/20260614-b4-disp-818d6bda-v1-1-cf39a3615085@proton.me
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/input/rmi4/rmi_f3a.c

Diff excerpt:

Not included in this email. See the upstream URL for the full patch.

Full patch:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=502ad7caaa1a445b734c827fa256e5311df67e3d

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DETAILED REPORT METHODOLOGY
======================================================================

The original Linux kernel CVE announcement for CVE-2026-64277 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64277

The original CVE announcement normally does not include a security-level
estimate. In particular, it may not contain a CVSS assessment, an impact
level, or enough information to determine whether the reported bug is a
practically relevant security issue. One purpose of this parallel CVE list
is to provide that missing technical and prioritization information.

The original goal of the AL-KERNEL project was to prioritize Linux kernel
CVE analysis automatically before manual review. The system can also help
identify non-security issues that may be suitable for automatic closure.

This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin.

The first analysis stage combines an autonomous classifier with additional
LLM-based analysis. The autonomous classifier runs locally on a CPU and is
based on a backpropagation neural network. Together, these mechanisms
produce a technical vulnerability description, identify likely weakness
types, estimate CVSS severity, and provide input for ActionableScore.

Two CVSS estimates are retained because incomplete kernel vulnerability
information often permits more than one defensible interpretation:

  Conservative CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7

The conservative vector represents a lower-impact interpretation.
The Best/paranoid vector intentionally represents a plausible upper-bound
interpretation and should not automatically be treated as demonstrated
real-world impact.

CVSS may also need to be adjusted for a particular Linux deployment,
because actual reachability, privileges, enabled kernel configuration,
hardware, namespaces, exposed device nodes, and other environmental
conditions can differ significantly between systems.

A separate ActionableScore mechanism evaluates practical remediation
urgency. Its analysis may include reachability, attack prerequisites,
subsystem exposure, memory-corruption characteristics, denial-of-service
reliability, and possible confidentiality, integrity, or
privilege-escalation impact.

  Conservative ActionableScore: 6
  Paranoid ActionableScore: 7

The final base severity is taken directly from the second tab-separated
field of the AL-KERNEL classification result. ActionableScore does not
replace or independently override that final AL-KERNEL decision, and
if ActionableScore adjusted impact level of ALKERNEL, then you would see
self-readable flags above like INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7.

For an AL-KERNEL result of MODERATE, this report uses the following
additional presentation split:

  ActionableScore below 5   -> MODERATE REGULAR
  ActionableScore 5 or more -> MODERATE 7.0

The distinction between MODERATE REGULAR and MODERATE 7.0 makes it
possible to identify Moderate issues that should receive manual analysis
and fixes before lower-priority MODERATE REGULAR issues. In many cases,
MODERATE REGULAR fixes may wait for a later rebase or routine update.

There is one override in which MODERATE REGULAR becomes MODERATE 7.0
even when the ActionableScore is below 5. When the AL-KERNEL result
contains the KPANIC flag, a MODERATE result is always presented as
MODERATE 7.0. The KPANIC flag selected with few regexps without
usage of AI at all, so it helps to detect cases when Kernel Crash happens
and similar (to filter False-Negative results from the LLM usage).

KPANIC indicates that a reliable kernel crash, kernel panic, or similarly
serious kernel availability impact was identified by the classification
workflow.

AL-KERNEL base severity for this report: IMPORTANT
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): IMPORTANT

These results are intended to support engineering triage. They are
machine-generated estimates, and cases marked for manual review should
be validated by a human security engineer before final disposition.
For more info read docs linked from here: https://kernelcve.org/
(and you can submit you own patch there to generate such a report
for non-existant CVE-id yet).

Note that in many cases this AI tool selects higher severity, than
real is (means you can expect Importants instead of Moderate 7.0 or
Moderates 7.0 instead of regular Moderates). If you see such cases,
please use reply email interface to add additional manual analyses
info to this particular CVE.
And please, please, let me know when you see Lows instead of Importants
or Important instead of Low (because particular for such cases I
need to tune this AI tool to make it better for this one and next similar).
My contact email for such notifications is alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).