CVE-2025-40114: Linux Kernel Array Bounds Vulnerability

CVE-2025-40114 Overview

CVE-2025-40114 is an out-of-bounds read vulnerability in the Linux kernel's IIO (Industrial I/O) subsystem, specifically within the VEML6075 UV light sensor driver. The vulnerability exists in the veml6075_read_int_time_ms function where an array bounds check is missing, allowing an index calculated by veml6075_read_int_time_index to range from 0 to 7, while the veml6075_it_ms array only contains 5 elements. This mismatch can lead to out-of-bounds memory access when processing integration time values.

Critical Impact

A local attacker with low privileges could potentially exploit this vulnerability to read kernel memory beyond the intended array boundaries, leading to information disclosure, or cause system instability resulting in denial of service. The vulnerability affects systems utilizing the VEML6075 UV sensor driver.

Affected Products

• Linux Kernel (versions prior to security patches)
• Systems using the VEML6075 UV light sensor driver
• Embedded Linux systems with IIO subsystem light sensor support

Discovery Timeline

• April 18, 2025 - CVE-2025-40114 published to NVD
• October 01, 2025 - Last updated in NVD database

Technical Details for CVE-2025-40114

Vulnerability Analysis

This vulnerability is classified as CWE-129 (Improper Validation of Array Index), a common software weakness that occurs when an array index is not properly validated before being used to access array elements. In this case, the veml6075_it_ms array is defined with only 5 elements (indices 0-4), but the veml6075_read_int_time_index function can return values ranging from 0 to 7.

When a value of 5, 6, or 7 is returned and used as an index without proper bounds checking, the code attempts to read memory beyond the allocated array space. This constitutes an out-of-bounds read vulnerability. The issue was identified through static code analysis via Coverity (CID 1574309), which flagged the potential for overrunning the array at element index 7 (byte offset 31).

The vulnerability is characterized as hardening against potentially broken or malicious hardware—while the driver expects valid integration time index values, a malfunctioning or compromised sensor device could potentially provide unexpected values that trigger the out-of-bounds access.

Root Cause

The root cause of CVE-2025-40114 is the absence of input validation on the index value returned by veml6075_read_int_time_index before using it to access the veml6075_it_ms array. The array is statically allocated with 5 4-byte elements, but the index calculation logic can produce values up to 7, creating a 3-element gap where out-of-bounds access can occur.

The fix adds proper bounds checking to ensure the index value falls within the valid range (0-4) before array access, preventing the out-of-bounds read condition.

Attack Vector

The attack requires local access to the system with low privileges. An attacker would need to interact with a system that has the VEML6075 driver loaded and potentially manipulate hardware responses or sensor data to trigger the out-of-bounds read condition.

The vulnerability could be exploited through:

1. Physical access to manipulate the I2C communication with a malicious or modified VEML6075 sensor
2. Kernel module interaction that processes crafted integration time index values
3. Exploiting other vulnerabilities to inject malformed data into the driver's processing path

While the attack complexity is considered low once local access is achieved, the requirement for local access and specific hardware interaction limits the exposure surface. However, successful exploitation could lead to kernel memory disclosure or system crashes.

Detection Methods for CVE-2025-40114

Indicators of Compromise

• Unexpected kernel crashes or panics originating from the IIO light subsystem
• Kernel log messages indicating memory access violations in veml6075_read_int_time_ms or related functions
• Unusual I2C communication patterns with VEML6075 sensors
• Anomalous sensor reading requests with invalid integration time parameters

Detection Strategies

• Monitor kernel logs for out-of-bounds access warnings related to the IIO subsystem using dmesg or centralized logging
• Deploy SentinelOne Singularity Platform for real-time kernel-level monitoring and anomaly detection on Linux endpoints
• Implement SIEM rules to detect kernel panic events associated with the VEML6075 driver module
• Use kernel debugging tools like KASAN (Kernel Address Sanitizer) in development environments to catch out-of-bounds accesses

Monitoring Recommendations

• Enable kernel debugging options that can detect out-of-bounds memory accesses during runtime
• Monitor for unusual driver behavior or repeated sensor initialization failures
• Track system stability metrics on devices using VEML6075 sensors
• Review audit logs for unexpected interactions with the IIO subsystem character devices

How to Mitigate CVE-2025-40114

Immediate Actions Required

• Update the Linux kernel to the latest patched version containing the array bounds check fix
• If immediate patching is not possible, consider temporarily blacklisting the veml6075 driver module if the UV sensor is not critical to operations
• Restrict local access to systems with the vulnerable driver to trusted users only
• Monitor affected systems for signs of exploitation attempts

Patch Information

The Linux kernel development team has released patches that add proper bounds checking to the veml6075_read_int_time_ms function. The patches are available through the official kernel git repository and have been committed to stable kernel branches.

Available patches:

• Kernel Git Commit 18a08b5
• Kernel Git Commit 7a40b52
• Kernel Git Commit 9c40a68
• Kernel Git Commit ee735aa

The patches introduce validation logic that ensures the index value is within the valid array bounds before accessing the veml6075_it_ms array, effectively preventing the out-of-bounds read condition.

Workarounds

• Blacklist the veml6075 kernel module by adding blacklist veml6075 to /etc/modprobe.d/blacklist.conf if the sensor is not required
• Restrict physical access to I2C buses connected to VEML6075 sensors to prevent hardware-based manipulation
• Apply kernel hardening options that provide additional protection against out-of-bounds memory access
• Consider using kernel live patching solutions if available for your distribution to apply fixes without system reboot

# Temporarily blacklist the vulnerable driver module
echo "blacklist veml6075" | sudo tee /etc/modprobe.d/blacklist-veml6075.conf
sudo modprobe -r veml6075

# Verify the module is not loaded
lsmod | grep veml6075