CVE-2026-23029: Linux Kernel Memory Leak Vulnerability

CVE-2026-23029 Overview

CVE-2026-23029 is a memory leak vulnerability in the Linux kernel affecting the KVM (Kernel-based Virtual Machine) subsystem on LoongArch architecture. The vulnerability exists in the kvm_eiointc_destroy() function, which fails to properly free the kvm_device struct that was allocated during device creation via kvm_ioctl_create_device().

Critical Impact

This memory leak vulnerability can lead to gradual memory exhaustion on systems running KVM virtualization on LoongArch platforms, potentially impacting system stability and availability over time.

Affected Products

• Linux kernel with KVM support on LoongArch architecture
• Systems utilizing KVM EIOINTC (Extended I/O Interrupt Controller) devices
• Virtualization hosts running LoongArch-based KVM guests

Discovery Timeline

• 2026-01-31 - CVE CVE-2026-23029 published to NVD
• 2026-02-03 - Last updated in NVD database

Technical Details for CVE-2026-23029

Vulnerability Analysis

The vulnerability stems from improper resource cleanup in the KVM subsystem's EIOINTC device handling code. When a KVM device is created through the kvm_ioctl_create_device() function, memory is allocated for the kvm_device structure. The design contract expects that when kvm_device->destroy() is called (pointing to kvm_eiointc_destroy() for EIOINTC devices), this function should be responsible for freeing the associated kvm_device struct.

However, the kvm_eiointc_destroy() function was not properly implementing this cleanup, leaving the allocated kvm_device memory unreleased. This results in a memory leak that occurs each time an EIOINTC device is destroyed, which can happen during VM shutdown or device reconfiguration operations.

Root Cause

The root cause is a missing kfree() call in the kvm_eiointc_destroy() function. The function was designed to clean up resources associated with the EIOINTC device but omitted the final step of freeing the kvm_device structure itself. This oversight in the device destruction lifecycle results in orphaned memory allocations.

Attack Vector

As a memory leak vulnerability, the attack vector is primarily through sustained operations that repeatedly create and destroy EIOINTC devices in KVM on LoongArch systems. While this is not directly exploitable for code execution, an attacker with the ability to manage VMs on an affected system could potentially trigger resource exhaustion by repeatedly creating and destroying VMs or EIOINTC devices, leading to denial of service conditions.

The vulnerability requires local access to the system with permissions to manage KVM virtual machines. The impact is limited to availability concerns rather than confidentiality or integrity breaches.

Detection Methods for CVE-2026-23029

Indicators of Compromise

• Gradual increase in kernel memory usage on LoongArch KVM hosts
• Memory allocation failures in KVM-related operations over extended uptime periods
• Kernel warnings or OOM (Out of Memory) conditions on virtualization hosts
• Abnormal growth of slab allocations related to KVM device structures

Detection Strategies

• Monitor kernel memory usage patterns on LoongArch KVM hosts for unexpected growth trends
• Implement memory leak detection tools such as kmemleak to identify unreferenced kernel memory allocations
• Track VM creation and destruction cycles correlated with memory consumption metrics
• Use SentinelOne Singularity platform to monitor for unusual system resource consumption patterns

Monitoring Recommendations

• Deploy continuous memory monitoring on systems running KVM with LoongArch architecture
• Configure alerts for kernel memory usage exceeding baseline thresholds
• Implement regular system reboots as a temporary mitigation if patching is delayed
• Use kernel debugging tools to trace kvm_device allocations and deallocations

How to Mitigate CVE-2026-23029

Immediate Actions Required

• Update to a patched Linux kernel version that includes the fix for CVE-2026-23029
• Review and apply kernel updates from your Linux distribution's security repository
• Plan for system maintenance windows to apply kernel patches requiring reboot
• Monitor affected systems for memory exhaustion until patches can be applied

Patch Information

The fix for this vulnerability has been committed to the Linux kernel stable branches. The patch ensures that kvm_eiointc_destroy() properly frees the kvm_device struct when destroying EIOINTC devices.

The kernel patches are available at the following commit references:

• Kernel Git Commit 7d8553fc
• Kernel Git Commit e94ec966

Workarounds

• Schedule periodic reboots of affected KVM hosts to clear accumulated memory leaks until patching is complete
• Limit the frequency of VM creation and destruction operations on affected systems
• Monitor memory usage closely and implement automated alerts for memory pressure conditions
• Consider migrating critical workloads to non-LoongArch KVM hosts until patches are applied

# Configuration example
# Check current kernel version and verify if patch is needed
uname -r

# Update kernel on Debian/Ubuntu-based systems
sudo apt update && sudo apt upgrade linux-image-generic

# Update kernel on RHEL/CentOS-based systems
sudo yum update kernel

# Verify kmemleak is enabled for monitoring (requires CONFIG_DEBUG_KMEMLEAK)
cat /sys/kernel/debug/kmemleak