CVE-2026-23426: Linux Kernel Reference Leak Vulnerability

CVE-2026-23426 Overview

A device node reference leak vulnerability has been identified in the Linux kernel's drm/logicvc driver. The logicvc_drm_config_parse() function calls of_get_child_by_name() to locate the "layers" node but fails to properly release the reference when the operation completes. This memory leak can lead to resource exhaustion over time, particularly in systems that frequently parse device tree configurations.

Critical Impact

Repeated exploitation of this reference leak could lead to kernel memory exhaustion and system instability on affected Linux systems using the logicvc DRM driver.

Affected Products

• Linux kernel with drm/logicvc driver enabled
• Systems using Xylon LogiCVC display controller
• Embedded systems utilizing LogiCVC IP cores

Discovery Timeline

• 2026-04-03 - CVE CVE-2026-23426 published to NVD
• 2026-04-03 - Last updated in NVD database

Technical Details for CVE-2026-23426

Vulnerability Analysis

This vulnerability is a Memory Leak affecting the Linux kernel's Direct Rendering Manager (DRM) subsystem, specifically within the logicvc driver component. The logicvc driver provides support for the Xylon LogiCVC display controller, commonly used in FPGA-based embedded systems.

The root issue lies in improper reference counting for device tree node objects. When the kernel parses device tree configurations, it uses reference-counted node objects that must be explicitly released after use. The of_get_child_by_name() function increments the reference count of the returned node, creating an obligation for the caller to decrement it when finished.

In vulnerable versions, the logicvc_drm_config_parse() function acquires a reference to the "layers" child node but never releases it, causing the reference count to remain elevated indefinitely. Each invocation of this parsing function leaks one device node reference, which accumulates over the system's lifetime.

Root Cause

The vulnerability stems from missing cleanup code in the logicvc_drm_config_parse() function. When calling of_get_child_by_name() to retrieve the "layers" device tree node, the function obtains a reference-counted pointer. The Linux kernel's device tree API requires callers to call of_node_put() on nodes obtained through of_get_child_by_name() when they are no longer needed. The absence of this cleanup call results in the reference leak.

Attack Vector

The attack vector for this vulnerability is primarily local and requires specific system configurations. An attacker would need:

1. Access to a system running a Linux kernel with the logicvc DRM driver loaded
2. The ability to trigger device tree configuration parsing operations
3. Persistence to repeatedly trigger the leak until system resources are exhausted

While the immediate impact is limited to resource exhaustion, sustained exploitation could lead to denial of service conditions as kernel memory becomes depleted.

The fix implements the __free(device_node) cleanup attribute, which automatically releases the device node reference when the variable goes out of scope, ensuring proper resource management without requiring explicit cleanup calls at every function exit point.

Detection Methods for CVE-2026-23426

Indicators of Compromise

• Gradual increase in kernel memory usage over time on systems with logicvc driver
• Elevated device tree node reference counts observed through kernel debugging tools
• System instability or out-of-memory conditions in long-running embedded systems
• Abnormal behavior in /sys/kernel/debug/ entries related to device tree nodes

Detection Strategies

• Monitor kernel memory allocation patterns using tools like kmemleak or /proc/meminfo
• Enable kernel debugging options to track device tree node reference counts
• Implement alerting on unexpected kernel memory growth trends
• Review system logs for OOM (Out of Memory) killer activity on affected systems

Monitoring Recommendations

• Deploy kernel memory monitoring on systems using the logicvc DRM driver
• Establish baseline memory usage patterns to detect anomalous growth
• Configure alerts for sustained memory increases without corresponding workload changes
• Periodically audit loaded kernel modules to identify systems with the vulnerable driver

How to Mitigate CVE-2026-23426

Immediate Actions Required

• Identify all systems running Linux kernels with the drm/logicvc driver enabled
• Schedule kernel updates to apply the security patches
• Consider rebooting long-running systems to clear accumulated leaked references
• Monitor affected systems for memory exhaustion symptoms until patches are applied

Patch Information

The Linux kernel maintainers have released patches to address this vulnerability. The fix introduces the __free(device_node) cleanup attribute to automatically release the device node reference when the variable goes out of scope, eliminating the memory leak.

Patches are available through the following kernel git commits:

• Kernel Git Commit 0bd326df
• Kernel Git Commit 78e91e49
• Kernel Git Commit 87163025
• Kernel Git Commit b88f4991
• Kernel Git Commit f8a6eba2
• Kernel Git Commit fef0e649

Workarounds

• If the logicvc DRM driver is not required, consider blacklisting the module to prevent loading
• Implement scheduled system reboots to periodically clear leaked memory on critical systems
• Reduce the frequency of operations that trigger device tree configuration parsing
• Monitor and set memory usage thresholds to trigger alerts before system instability occurs

# Blacklist the logicvc module if not required
echo "blacklist logicvc" >> /etc/modprobe.d/blacklist-logicvc.conf

# Verify the module is not loaded
lsmod | grep logicvc

# Force module unload if currently loaded (requires no active users)
modprobe -r logicvc