CVE-2026-23178: Linux Kernel Buffer Overflow Vulnerability

CVE-2026-23178 Overview

A buffer overflow vulnerability has been identified in the Linux kernel's HID (Human Interface Device) subsystem, specifically within the i2c_hid_get_report() function of the i2c-hid driver. The vulnerability occurs when the i2c_hid_xfer function reads data into the ihid->rawbuf buffer without proper bounds checking. The recv_len parameter, which can originate from userspace via the hidraw driver, is bounded only by HID_MAX_BUFFER_SIZE (16384 bytes) by default. However, the destination buffer ihid->rawbuf has its size determined at runtime based on the maximum report size for the specific device, which can be significantly smaller than the maximum allowed input length.

Critical Impact

Potential buffer overflow in the Linux kernel i2c-hid driver could allow privileged local attackers with root access to hidraw devices to corrupt kernel memory, potentially leading to denial of service or privilege escalation.

Affected Products

• Linux kernel with i2c-hid driver enabled
• Systems using HID over I2C devices (common in laptops and embedded systems)
• Devices utilizing the hidraw interface

Discovery Timeline

• 2026-02-14 - CVE CVE-2026-23178 published to NVD
• 2026-02-18 - Last updated in NVD database

Technical Details for CVE-2026-23178

Vulnerability Analysis

The vulnerability resides in the i2c_hid_get_report() function within the Linux kernel's i2c-hid driver. When processing HID reports, the function utilizes i2c_hid_xfer to read recv_len + sizeof(__le16) bytes of data into the internal buffer ihid->rawbuf. The critical issue is a mismatch between the maximum allowed input size and the actual buffer capacity.

The recv_len parameter can be controlled through userspace via the hidraw driver interface. While this value is constrained by HID_MAX_BUFFER_SIZE (16384 bytes) by default, the i2c-hid driver does not set the optional max_buffer_size field in the struct hid_ll_driver that would further limit this value. Meanwhile, the destination buffer ihid->bufsize is dynamically allocated based on the maximum report size advertised by the specific HID device, which can be substantially smaller than 16384 bytes.

This size discrepancy creates a classic buffer overflow scenario where an attacker with access to the hidraw device can supply a recv_len value that exceeds the actual buffer capacity, causing memory corruption beyond the allocated buffer boundaries.

Root Cause

The root cause is insufficient bounds validation of the recv_len parameter before performing the I2C transfer operation. The driver fails to verify that the requested read length does not exceed the actual allocated buffer size (ihid->bufsize). The fix implements proper truncation of recv_len to ihid->bufsize - sizeof(__le16) to ensure the read operation cannot exceed the buffer boundaries.

Attack Vector

Exploitation of this vulnerability requires local access with root privileges to interact with hidraw devices. An attacker with such access could craft malicious HID report requests with oversized recv_len values through the hidraw interface. While the impact is limited by the requirement for root access, successful exploitation could lead to kernel memory corruption, potentially enabling denial of service or further privilege escalation within the kernel context.

The vulnerability mechanism involves manipulating the report request size through the hidraw interface to trigger the buffer overflow condition. Detailed technical information can be found in the Linux Kernel Patch 2124279f.

Detection Methods for CVE-2026-23178

Indicators of Compromise

• Kernel crash or panic events related to the i2c-hid driver or HID subsystem
• Unusual memory corruption signatures in kernel logs associated with HID devices
• Suspicious access patterns to /dev/hidraw* devices by unexpected processes

Detection Strategies

• Monitor kernel logs for oops or panic messages referencing i2c_hid_get_report, i2c_hid_xfer, or related HID subsystem functions
• Implement file integrity monitoring on critical kernel modules, particularly i2c-hid.ko
• Use kernel auditing to track access to hidraw device nodes by non-standard applications

Monitoring Recommendations

• Enable kernel crash dump collection (kdump) to capture memory state during any exploitation attempts
• Implement alerting on kernel ring buffer messages containing references to buffer overflow or memory corruption in HID-related code paths
• Monitor for unusual patterns of hidraw device access, especially large report requests

How to Mitigate CVE-2026-23178

Immediate Actions Required

• Update the Linux kernel to a patched version that includes the buffer overflow fix
• Restrict access to /dev/hidraw* devices to only necessary users and applications
• Review and audit any custom applications that interact with hidraw interfaces

Patch Information

The Linux kernel development team has released patches across multiple stable kernel branches to address this vulnerability. The fix implements proper truncation of recv_len to ensure it does not exceed the allocated buffer size. The following patches are available:

• Linux Kernel Patch 2124279f
• Linux Kernel Patch 2497ff3
• Linux Kernel Patch 786ec17
• Linux Kernel Patch cff3f61
• Linux Kernel Patch f9c9ad8

Workarounds

• Restrict access to hidraw devices using udev rules to limit which users can interact with these devices
• Consider disabling the i2c-hid driver (i2c_hid) via kernel module blacklisting if HID over I2C functionality is not required
• Implement SELinux or AppArmor policies to control access to hidraw device nodes

# Restrict hidraw device access via udev rules
# Create /etc/udev/rules.d/99-hidraw-restrict.rules
KERNEL=="hidraw*", MODE="0600", OWNER="root", GROUP="root"

# Blacklist i2c-hid module if not needed
# Add to /etc/modprobe.d/blacklist-i2c-hid.conf
echo "blacklist i2c_hid" >> /etc/modprobe.d/blacklist-i2c-hid.conf
echo "blacklist i2c_hid_acpi" >> /etc/modprobe.d/blacklist-i2c-hid.conf