CVE-2025-71136: Linux Kernel Buffer Overflow Vulnerability

CVE-2025-71136 Overview

A vulnerability has been discovered in the Linux kernel's adv7842 media driver that could allow out-of-bounds array accesses. The flaw exists in the adv7842_cp_log_status() function where error return values from cp_read() and hdmi_read() functions are improperly handled. When these functions return -EIO (I/O error), the negative value is subsequently used as an array index, potentially leading to out-of-bounds memory access.

This vulnerability was discovered by the Linux Verification Center (linuxtesting.org) using the SVACE static analysis tool.

Critical Impact
Out-of-bounds array access in kernel space can lead to system instability, information disclosure, or potential privilege escalation depending on how the accessed memory is utilized.

Affected Products

Linux kernel with adv7842 media driver enabled
Systems utilizing Analog Devices ADV7842 video receiver hardware
Embedded systems and media processing platforms with ADV7842 chipset support

Discovery Timeline

2026-01-14 - CVE CVE-2025-71136 published to NVD
2026-01-19 - Last updated in NVD database

Technical Details for CVE-2025-71136

Vulnerability Analysis

The vulnerability resides in the adv7842_cp_log_status() function within the ADV7842 media driver. This driver provides support for the Analog Devices ADV7842 high performance video receiver chip, commonly used in multimedia applications for HDMI/component video processing.

The core issue stems from insufficient validation of return values from I2C read operations. The cp_read() and hdmi_read() helper functions perform I2C bus transactions to communicate with the ADV7842 hardware. Under certain error conditions (such as bus communication failures), these functions return -EIO, which is the negative error code for I/O errors in the Linux kernel.

The problematic code path uses these return values directly as array indices without checking for negative values first. In C, using a negative value as an array index results in accessing memory locations before the intended array boundary, which constitutes an out-of-bounds read operation.

Root Cause

The root cause is improper input validation of I2C read operation return values. The cp_read() and hdmi_read() functions can return negative error codes when hardware communication fails, but the code in adv7842_cp_log_status() did not account for this possibility before using the values as array indices. This is a classic example of failing to validate error conditions in driver code that interfaces with potentially unreliable hardware.

Attack Vector

The attack vector for this vulnerability requires local access and the ability to trigger I/O errors on the I2C bus connected to the ADV7842 device. Potential exploitation scenarios include:

Physical access to manipulate the I2C bus or ADV7842 hardware
Triggering race conditions or timing issues that cause I2C communication failures
Exploiting other vulnerabilities to cause I/O errors during driver status logging operations

The vulnerability is triggered when the kernel attempts to log the status of the ADV7842 device while I2C communication errors occur, causing negative error codes to be used as array indices.

Detection Methods for CVE-2025-71136

Indicators of Compromise

Kernel log messages indicating unusual behavior in the adv7842 driver
Unexpected kernel panics or oops messages referencing the adv7842 module
System instability when accessing video capture functionality
Memory corruption indicators in kernel space

Detection Strategies

Monitor kernel logs for out-of-bounds access warnings related to the adv7842 driver
Enable kernel address sanitizer (KASAN) to detect out-of-bounds memory accesses in development/testing environments
Implement I2C bus monitoring for abnormal error patterns
Review dmesg output for adv7842-related error messages during video capture operations

Monitoring Recommendations

Configure alerting on kernel oops or panic events involving media drivers
Enable kernel auditing for driver module loading and unloading
Monitor system stability metrics on systems with ADV7842 hardware
Implement hardware health monitoring for I2C bus integrity

How to Mitigate CVE-2025-71136

Immediate Actions Required

Update to a patched Linux kernel version that includes the fix
If updates are not immediately possible, consider disabling the adv7842 driver module if not required
Restrict physical access to systems with ADV7842 hardware
Monitor affected systems for signs of exploitation or instability

Patch Information

The fix has been applied to multiple stable Linux kernel branches. The patch adds proper validation of return values from cp_read() and hdmi_read() before using them as array indices. The following kernel commits contain the fix:

Workarounds

Blacklist the adv7842 kernel module if the ADV7842 hardware is not in use: add blacklist adv7842 to /etc/modprobe.d/blacklist.conf
Implement access controls to limit who can interact with video capture devices
Monitor systems for unusual I2C bus activity or hardware faults
Consider network isolation for affected embedded systems until patches can be applied

bash

# Disable the adv7842 driver module temporarily
sudo modprobe -r adv7842

# Blacklist the module to prevent automatic loading
echo "blacklist adv7842" | sudo tee /etc/modprobe.d/blacklist-adv7842.conf

# Update initramfs to persist the blacklist
sudo update-initramfs -u