CVE-2026-23027: Linux Kernel Memory Leak Vulnerability

CVE-2026-23027 Overview

CVE-2026-23027 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_pch_pic_destroy() function, which fails to properly free the kvm_device structure that was allocated during device creation via kvm_ioctl_create_device().

When a KVM device is created, memory is allocated for the kvm_device struct. The destroy() callback function is expected to release this memory when the device is destroyed. However, the kvm_pch_pic_destroy() implementation was missing the necessary deallocation logic, resulting in a memory leak each time a PCH-PIC (Platform Controller Hub Programmable Interrupt Controller) device is destroyed.

Critical Impact

Memory leak in KVM device destruction can lead to gradual system resource exhaustion on virtualization hosts running LoongArch-based virtual machines.

Affected Products

• Linux kernel with KVM support for LoongArch architecture
• LoongArch-based virtualization hosts using KVM
• Systems utilizing KVM PCH-PIC device emulation

Discovery Timeline

• 2026-01-31 - CVE CVE-2026-23027 published to NVD
• 2026-02-03 - Last updated in NVD database

Technical Details for CVE-2026-23027

Vulnerability Analysis

This vulnerability is classified as a Memory Leak within the Linux kernel's KVM virtualization subsystem. The issue affects the LoongArch architecture-specific implementation of the PCH-PIC interrupt controller emulation used in virtualized environments.

The memory leak occurs in the resource cleanup path of the KVM device lifecycle. When virtual machines are created and destroyed, particularly those utilizing the PCH-PIC interrupt controller emulation, the associated kvm_device structures are not properly deallocated. Over time, this can accumulate and consume significant amounts of kernel memory.

While this vulnerability does not directly enable code execution or privilege escalation, persistent memory leaks in kernel space can lead to system instability, denial of service conditions, and potential security implications as available memory decreases.

Root Cause

The root cause of this vulnerability is an incomplete implementation of the kvm_pch_pic_destroy() function. When kvm_ioctl_create_device() is called to create a new KVM device, it allocates memory for the kvm_device structure. The corresponding destroy() callback, implemented as kvm_pch_pic_destroy() for PCH-PIC devices, is responsible for releasing this allocated memory.

However, the original implementation of kvm_pch_pic_destroy() did not include the necessary call to free the kvm_device struct, violating the expected memory management contract between the KVM core and architecture-specific device implementations.

Attack Vector

The attack vector for this vulnerability is primarily local and requires the ability to create and destroy KVM virtual machines on an affected LoongArch system. An attacker with local access and permissions to manage virtual machines could potentially exploit this vulnerability to exhaust system memory by repeatedly creating and destroying VMs with PCH-PIC devices configured.

The exploitation scenario involves:

1. An attacker gains access to a system with KVM management permissions
2. The attacker repeatedly creates and destroys virtual machines utilizing PCH-PIC device emulation
3. Each destruction cycle leaks memory from the kvm_device structure
4. Over time, kernel memory is exhausted, potentially causing system instability or denial of service

Detection Methods for CVE-2026-23027

Indicators of Compromise

• Gradual increase in kernel memory usage on KVM hosts running LoongArch VMs
• Memory consumption that does not decrease after VM destruction
• System logs indicating memory pressure or out-of-memory conditions on virtualization hosts
• Unexpected kernel slab memory growth in KVM-related allocations

Detection Strategies

• Monitor kernel memory utilization using tools like slabtop to identify growing KVM-related memory allocations
• Implement memory profiling on KVM hosts to track kvm_device structure allocations and deallocations
• Use kernel memory debugging features (KASAN, KMEMLEAK) during development and testing to identify unreleased memory
• Deploy monitoring for abnormal kernel memory growth patterns on LoongArch virtualization infrastructure

Monitoring Recommendations

• Set up alerts for kernel memory utilization thresholds on KVM hosts
• Implement periodic memory auditing on systems running LoongArch-based virtual machines
• Monitor VM lifecycle events and correlate with memory consumption patterns
• Enable kernel memory leak detection tools in non-production environments to proactively identify similar issues

How to Mitigate CVE-2026-23027

Immediate Actions Required

• Update the Linux kernel to a patched version that includes the fix for kvm_pch_pic_destroy()
• Restart KVM services or reboot affected hosts after applying the kernel update to clear any existing leaked memory
• Limit VM creation and destruction frequency on unpatched systems to reduce memory leak impact
• Monitor memory usage closely on systems that cannot be immediately patched

Patch Information

The Linux kernel development team has released patches to address this vulnerability. The fix ensures that the kvm_device struct is properly freed in the kvm_pch_pic_destroy() function.

Relevant kernel commits:

• Linux Kernel Commit Review
• Linux Kernel Commit Changes

System administrators should update to the latest stable kernel version that includes these commits.

Workarounds

• Reduce the frequency of VM creation and destruction cycles on affected systems
• Implement scheduled system reboots during maintenance windows to clear accumulated leaked memory
• Consider temporarily disabling PCH-PIC device emulation if not required for workloads
• Isolate critical workloads from systems with high VM turnover rates until patches can be applied

# Check current kernel version
uname -r

# Monitor kernel memory usage for leaks
watch -n 5 'cat /proc/meminfo | grep -E "Slab|KReclaimable"'

# Use slabtop to monitor slab allocations
slabtop -o | head -20