CVE-2026-31768: Linux Kernel Buffer Overflow Vulnerability

CVE-2026-31768 Overview

CVE-2026-31768 is a Linux kernel vulnerability in the ti-adc161s626 Industrial I/O (IIO) analog-to-digital converter driver. The driver passed a stack-allocated buffer to spi_read(), violating the kernel requirement that all Serial Peripheral Interface (SPI) buffers must be DMA-safe. The fix introduces a dedicated DMA-safe buffer and uses a u8[] array instead of __be16 and __be32 types, with corresponding conversion logic.

Critical Impact
Local attackers with low privileges can leverage DMA operations against unsafe stack memory to corrupt kernel state, potentially leading to memory disclosure, integrity loss, or denial of service.

Affected Products

Linux kernel versions containing the drivers/iio/adc/ti-adc161s626.c driver prior to the fix
Systems using the Texas Instruments ADC161S626 ADC over SPI
Embedded and industrial Linux deployments leveraging IIO ADC subsystems

Discovery Timeline

2026-05-01 - CVE-2026-31768 published to the National Vulnerability Database (NVD)
2026-05-03 - Last updated in NVD database

Technical Details for CVE-2026-31768

Vulnerability Analysis

The ti-adc161s626 IIO ADC driver issued spi_read() calls using a buffer allocated on the kernel stack. The Linux SPI subsystem requires that all transfer buffers reside in DMA-safe memory because controllers may perform Direct Memory Access (DMA) directly into the supplied buffer. Stack memory is not guaranteed to be DMA-coherent and may share cache lines with adjacent kernel data.

When DMA is used against a non-DMA-safe stack buffer, cache management operations can corrupt neighboring stack contents or expose stale data. This creates conditions for kernel memory corruption and potential information disclosure on systems where the controller falls back to DMA transfers.

Root Cause

The root cause is improper buffer placement for SPI transfers. The driver used __be16 and __be32 typed variables on the stack to receive ADC samples. These were passed directly to spi_read() without allocating from a DMA-coherent region. The fix replaces these with a u8[] buffer allocated alongside device state, ensuring DMA safety, and adjusts byte-swap conversion accordingly.

Attack Vector

Exploitation requires local access with low privileges to interact with the affected IIO device or trigger ADC reads through sysfs or /dev/iio:deviceX interfaces. An attacker capable of inducing repeated SPI transfers may force DMA-driven memory corruption against the kernel stack. The vulnerability is not remotely exploitable and requires the affected driver to be loaded and bound to hardware.

No public proof-of-concept exploit is available. The remediation is delivered as a series of stable kernel commits referenced in the Kernel Git Commit b3bb8fa and related backports.

Detection Methods for CVE-2026-31768

Indicators of Compromise

Unexpected kernel oops or stack corruption messages referencing ti-adc161s626 or spi_read in dmesg
Sporadic ADC read failures or implausible sample values from IIO device nodes
KASAN (Kernel Address Sanitizer) reports flagging stack-out-of-bounds writes during SPI transfers

Detection Strategies

Inventory kernel versions across embedded and industrial Linux fleets to identify hosts running pre-patch builds with the ti-adc161s626 driver enabled
Audit lsmod output and /sys/bus/iio/devices/ entries to determine where the vulnerable driver is loaded
Correlate kernel log anomalies with userspace processes accessing IIO ADC sysfs attributes

Monitoring Recommendations

Forward dmesg and /var/log/kern.log to a centralized logging platform and alert on SPI or IIO subsystem errors
Track local privilege boundaries and unexpected access patterns to /dev/iio:device* nodes
Monitor kernel package versions through configuration management to detect drift from patched baselines

How to Mitigate CVE-2026-31768

Immediate Actions Required

Apply the latest stable Linux kernel update from your distribution that includes the upstream fix for the ti-adc161s626 driver
Restrict local access on systems exposing IIO ADC interfaces, particularly multi-tenant or shared embedded platforms
Where the driver is unused, unload or blacklist ti-adc161s626 to remove the attack surface

Patch Information

The upstream resolution is distributed across multiple stable branches. Refer to the merged commits: Kernel Git Commit 014c6d2, Kernel Git Commit 67b3a91, Kernel Git Commit 7684615, Kernel Git Commit b3bb8fa, Kernel Git Commit d2d031b, and Kernel Git Commit fa64aab. Track your distribution's security advisories for backported package versions.

Workarounds

Blacklist the ti-adc161s626 module on systems that do not require the ADC functionality by adding blacklist ti-adc161s626 to /etc/modprobe.d/
Tighten file permissions on /sys/bus/iio/ and /dev/iio:device* to limit access to trusted service accounts
Apply mandatory access controls such as SELinux or AppArmor profiles to constrain processes that interact with IIO devices

bash

# Configuration example: blacklist the vulnerable driver until patched
echo "blacklist ti-adc161s626" | sudo tee /etc/modprobe.d/cve-2026-31768.conf
sudo modprobe -r ti-adc161s626
sudo update-initramfs -u