CVE-2026-56936: Wacom HID Driver Privilege Escalation Flaw

CVE-2026-56936 Overview

CVE-2026-56936 is an out-of-bounds write vulnerability in the wacom_hid_set_device_mode function of wacom_sys.c, a component of the Linux kernel Wacom HID driver shipped with Android. The flaw stems from a missing bounds check [CWE-119] that allows memory corruption outside intended buffer boundaries. Successful exploitation leads to local privilege escalation on affected devices without requiring user interaction or additional execution privileges. The vulnerability requires physical access to the target device, which limits remote exploitation potential but remains relevant for lost, stolen, or shared hardware scenarios. Google disclosed the issue in the Android Security Bulletin for October 2026.

Critical Impact
Attackers with physical access to a vulnerable Android device can trigger an out-of-bounds write in the kernel-space Wacom HID driver, resulting in privilege escalation without user interaction.

Affected Products

Android devices using the Wacom HID driver (wacom_sys.c)
Pixel devices covered by the October 2026 Android Security Bulletin
Linux kernel builds shipping the vulnerable wacom_hid_set_device_mode implementation

Discovery Timeline

2026-10-06 - CVE-2026-56936 published to NVD
2026-10-06 - Last updated in NVD database
October 2026 - Addressed in the Android Security Bulletin

Technical Details for CVE-2026-56936

Vulnerability Analysis

The vulnerability resides in wacom_hid_set_device_mode, a function responsible for configuring the operating mode of connected Wacom HID devices. The function writes data to a buffer without validating that the write operation stays within allocated bounds. Because the driver executes in kernel context, memory corruption in this path can overwrite adjacent kernel structures.

An attacker who connects a crafted USB or HID peripheral that imitates a Wacom device can trigger the vulnerable code path during device initialization. The resulting out-of-bounds write enables tampering with kernel objects used for access control, allowing escalation from an unprivileged context to kernel-level privileges.

Exploitation does not require interaction from the device user. The attack succeeds the moment the malicious peripheral is enumerated by the kernel.

Root Cause

The root cause is a missing bounds check prior to a write operation inside wacom_hid_set_device_mode. The function trusts input associated with the HID device descriptor and copies or writes data without validating the length against the destination buffer size. This is a classic improper restriction of operations within the bounds of a memory buffer, categorized as [CWE-119].

Attack Vector

The attack vector is physical. An adversary must connect a malicious or specially crafted HID device, typically over USB, to the target Android system. Once attached, the kernel driver processes the device descriptor and invokes the vulnerable function, triggering memory corruption that leads to privilege escalation. Refer to the Android Security Bulletin October 2026 for additional technical context.

Detection Methods for CVE-2026-56936

Indicators of Compromise

Unexpected kernel oops or panic entries referencing wacom_hid_set_device_mode or wacom_sys in dmesg output.
Enumeration of unknown or unauthorized USB HID devices in system logs shortly before privilege escalation events.
Unexpected processes running with elevated UID or capabilities following a peripheral connection.

Detection Strategies

Monitor kernel logs for crashes, memory corruption warnings, or KASAN reports originating in the Wacom driver code path.
Inspect USB device enumeration events for HID devices that claim Wacom vendor or product identifiers but originate from untrusted sources.
Correlate peripheral attachment events with subsequent privilege transitions in audit logs.

Monitoring Recommendations

Enable USB device auditing to log vendor ID, product ID, and attachment timestamps.
Collect kernel ring buffer output centrally and alert on faults within HID drivers.
Track Android Security Patch Level (SPL) across the fleet to confirm devices receive the October 2026 patch.

How to Mitigate CVE-2026-56936

Immediate Actions Required

Apply the October 2026 Android security patch level or later to all affected devices.
Restrict physical access to critical Android devices, particularly those used for administrative or privileged workflows.
Disable or restrict unused USB ports and HID device attachment on managed endpoints where feasible.

Patch Information

Google addressed CVE-2026-56936 in the Android Security Bulletin for October 2026. Device owners should install updates that advertise the 2026-10-01 or later Android Security Patch Level. Pixel-specific fixes are documented in the Android Security Bulletin October 2026.

Workarounds

Enforce physical security policies to prevent attackers from attaching unauthorized peripherals.
Deploy mobile device management (MDM) policies that disable USB data transfer or restrict HID peripheral classes on managed devices.
Power off devices or enable lockdown mode when leaving them unattended in untrusted environments.

bash

# Verify installed Android Security Patch Level on a device
adb shell getprop ro.build.version.security_patch