CVE-2026-23431: Linux Kernel Memory Leak Vulnerability

CVE-2026-23431 Overview

A memory leak vulnerability has been discovered in the Linux kernel's Amlogic SPI driver (amlogic-spisg). The vulnerability exists in the aml_spisg_probe() function, where the SPI controller object (ctlr) allocated by spi_alloc_target() or spi_alloc_host() fails to be properly released via spi_controller_put() in several error paths during driver initialization.

Critical Impact

This memory leak can lead to resource exhaustion on systems utilizing Amlogic SPI hardware when the driver repeatedly fails to probe, potentially causing system instability or denial of service conditions over time.

Affected Products

• Linux kernel with Amlogic SPI driver (amlogic-spisg)
• Systems utilizing Amlogic SoC SPI interfaces
• Embedded devices with Amlogic chipsets

Discovery Timeline

• 2026-04-03 - CVE CVE-2026-23431 published to NVD
• 2026-04-07 - Last updated in NVD database

Technical Details for CVE-2026-23431

Vulnerability Analysis

The vulnerability is classified as a Memory Leak, a type of resource management error that occurs when dynamically allocated memory is not properly freed after use. In the context of this Linux kernel driver, the aml_spisg_probe() function is responsible for initializing the Amlogic SPI controller during device enumeration.

During the probe sequence, the driver allocates a controller structure using spi_alloc_target() or spi_alloc_host(). These allocation functions create a reference-counted object that requires explicit cleanup via spi_controller_put() when no longer needed. The vulnerability arises because multiple error handling paths in the probe function fail to call spi_controller_put() before returning, leaving the allocated memory orphaned.

This issue is particularly problematic in embedded systems where memory is constrained, or in scenarios where the driver is repeatedly loaded and unloaded (such as during development or testing), or when hardware issues cause repeated probe failures.

Root Cause

The root cause is improper resource management in the driver's error handling logic. When aml_spisg_probe() encounters an error after the initial SPI controller allocation but before successful registration, it returns an error code without first releasing the allocated controller object. The kernel's reference counting mechanism expects drivers to explicitly call spi_controller_put() to decrement the reference count and trigger cleanup when initialization fails.

The fix converts the allocation calls to use the device-managed variants devm_spi_alloc_host() and devm_spi_alloc_target(). These devm (device-managed) functions automatically tie the resource lifecycle to the device object, ensuring proper cleanup when the device is removed or when probe fails, eliminating the manual cleanup requirement.

Attack Vector

This vulnerability has a local attack vector and requires the ability to influence driver behavior or trigger repeated probe failures. The exploitation scenario involves causing the Amlogic SPI driver to repeatedly fail during initialization after allocating the controller object.

While direct exploitation for code execution is not feasible with this memory leak, an attacker with local access could potentially:

1. Trigger repeated driver load/unload cycles that fail at specific points
2. Cause hardware faults or configuration errors that lead to probe failures
3. Gradually exhaust kernel memory, leading to system degradation or denial of service

The practical exploitability is limited as it requires physical access to the system or privileged operations to manipulate driver behavior.

Detection Methods for CVE-2026-23431

Indicators of Compromise

• Unusual kernel memory growth over time on systems with Amlogic SPI hardware
• Repeated SPI driver probe failure messages in kernel logs (dmesg)
• System memory exhaustion without corresponding userspace memory usage
• Kernel slab allocator statistics showing unreleased SPI-related objects

Detection Strategies

• Monitor kernel memory usage trends using tools like /proc/meminfo and /proc/slabinfo
• Implement kernel log monitoring for repeated aml_spisg_probe failure patterns
• Use kernel memory leak detection tools such as kmemleak to identify orphaned allocations
• Deploy SentinelOne Singularity platform for endpoint monitoring and anomaly detection

Monitoring Recommendations

• Configure alerts for kernel memory pressure events on affected systems
• Enable kernel memory debugging options (CONFIG_DEBUG_KMEMLEAK) in development environments
• Monitor system uptime correlation with memory consumption on embedded Amlogic devices
• Review kernel logs periodically for driver initialization failures

How to Mitigate CVE-2026-23431

Immediate Actions Required

• Update the Linux kernel to a patched version containing the fix
• Review systems using Amlogic SPI hardware for signs of memory exhaustion
• Consider temporarily disabling the amlogic-spisg driver if not required and patching is delayed
• Monitor affected systems for resource exhaustion until patches can be applied

Patch Information

The vulnerability has been resolved in the upstream Linux kernel. The fix converts the manual memory management to device-managed allocation, ensuring proper cleanup regardless of the error path taken during probe.

Patches are available in the following kernel commits:

• Kernel Git Commit 8e28a01b69f7
• Kernel Git Commit b8db9552997924b7
• Kernel Git Commit bec21d97c968a480

Apply the appropriate patch for your kernel version by updating to a release that includes these commits.

Workarounds

• If patching is not immediately possible, disable the amlogic-spisg module via kernel configuration or blacklisting
• Implement system monitoring to detect and respond to memory exhaustion conditions
• Schedule regular system reboots on embedded devices as a temporary mitigation to clear leaked memory
• Consider using custom kernel builds with the patch backported for critical deployments

# Blacklist the amlogic-spisg driver temporarily until patched
echo "blacklist amlogic-spisg" >> /etc/modprobe.d/blacklist-amlogic-spi.conf
# Rebuild initramfs if the module is loaded early
update-initramfs -u