CVE-2026-43476: Linux Kernel Buffer Overflow Vulnerability

CVE-2026-43476 Overview

CVE-2026-43476 is a Linux kernel vulnerability in the Industrial I/O (IIO) chemical sensor driver sps30_i2c. The flaw resides in the sps30_i2c_read_meas() function, where sizeof(num) evaluates to sizeof(size_t) (8 bytes on 64-bit systems) instead of the intended __be32 element size (4 bytes). This buffer size miscalculation causes the driver to read or process more data than allocated for the measurement buffer, producing incorrect sensor readings and potential out-of-bounds memory access. The fix replaces the incorrect expression with sizeof(*meas) to correctly match the buffer element type.

Critical Impact

Incorrect buffer sizing in the sps30 particulate matter sensor driver can cause out-of-bounds memory reads and incorrect sensor measurements on systems exposing this I2C device.

Affected Products

• Linux kernel versions containing the iio/chemical/sps30_i2c driver prior to the patched commits
• Distributions shipping vulnerable stable kernel branches referenced in the upstream fix series
• Embedded and IoT systems using the Sensirion SPS30 particulate matter sensor over I2C

Discovery Timeline

• 2026-05-13 - CVE-2026-43476 published to NVD
• 2026-05-13 - Last updated in NVD database

Technical Details for CVE-2026-43476

Vulnerability Analysis

The vulnerability is a boundary condition error in the sps30_i2c_read_meas() function of the Linux kernel IIO chemical sensor subsystem. The driver retrieves measurement data from the Sensirion SPS30 sensor over the I2C bus and decodes the response into an array of big-endian 32-bit integers (__be32). The buffer length calculation used the wrong reference type, leading to a size computation that does not match the actual element width on 64-bit architectures.

On 64-bit systems, sizeof(num) resolves to 8 bytes because num is declared as size_t. The intended element size of __be32 is 4 bytes. This mismatch causes loops or memory operations driven by the size value to overshoot the buffer's true element width, resulting in misaligned reads and incorrect interpretation of sensor data.

Root Cause

The root cause is the use of sizeof(num) where num is a size_t variable rather than the target buffer element. The intent was to express the size of one __be32 element within the measurement buffer. The corrected code uses sizeof(*meas), which dereferences the buffer pointer and yields the element type's actual size. This pattern aligns with idiomatic kernel coding for size calculations tied to the buffer being processed.

Attack Vector

Exploitation requires access to a system with the sps30_i2c driver loaded and an attached or emulated SPS30 sensor on the I2C bus. The defect is primarily reachable by local processes interacting with the IIO sysfs or character device interfaces, or by malformed sensor responses on the I2C link. Network attack vectors are not applicable. The practical impact centers on data integrity of sensor measurements and possible out-of-bounds memory access within the kernel address space.

No verified public exploit code is available for this issue. The vulnerability is documented through upstream kernel commits referenced in the Linux Kernel Commit 165f12b4 and related stable backports.

Detection Methods for CVE-2026-43476

Indicators of Compromise

• Anomalous or implausible particulate matter readings reported by IIO sysfs entries for the SPS30 device
• Kernel log entries referencing sps30_i2c with measurement decoding errors or unexpected values
• Crashes or KASAN reports implicating sps30_i2c_read_meas() on systems with the affected driver loaded

Detection Strategies

• Inventory running kernel versions across endpoints and IoT assets and compare against the patched stable releases referenced in the upstream commits
• Enable Kernel Address Sanitizer (KASAN) in test environments to surface out-of-bounds accesses in the IIO chemical sensor path
• Audit loaded kernel modules with lsmod | grep sps30 to identify systems exposing the vulnerable driver

Monitoring Recommendations

• Centralize kernel logs (dmesg, journalctl -k) and alert on warnings or oopses originating from IIO chemical drivers
• Track kernel package versions through configuration management and flag hosts running pre-patch builds
• Monitor changes to /sys/bus/iio/devices/ entries associated with the SPS30 sensor for unexpected readings or driver re-initialization

How to Mitigate CVE-2026-43476

Immediate Actions Required

• Apply the upstream kernel patch series that replaces sizeof(num) with sizeof(*meas) in sps30_i2c_read_meas()
• Update to a stable Linux kernel build that includes the referenced fix commits from kernel.org
• Restrict local access to the IIO interface on hosts that cannot be patched immediately

Patch Information

The fix has been merged across multiple stable branches. Review and apply the upstream commits: Linux Kernel Commit 08881d82, Linux Kernel Commit 165f12b4, Linux Kernel Commit 216345f9, Linux Kernel Commit 2a4d111a, Linux Kernel Commit 90e978ac, Linux Kernel Commit 9aff2e9c, and Linux Kernel Commit dcdf1e92.

Workarounds

• Unload the sps30_i2c module on systems that do not require SPS30 sensor functionality using modprobe -r sps30_i2c
• Blacklist the driver in /etc/modprobe.d/ to prevent automatic loading until the kernel is patched
• Restrict permissions on the corresponding /sys/bus/iio/devices/ paths to limit unprivileged interaction with the sensor

# Blacklist the vulnerable driver until the kernel is patched
echo "blacklist sps30_i2c" | sudo tee /etc/modprobe.d/blacklist-sps30.conf
sudo modprobe -r sps30_i2c