CVE-2026-53019: Linux Kernel SpaceMIT CCU Clock Logic Bug Kernel Panic

Technical summary

CVE-2026-53019 is a logic bug in the Linux kernel's SpaceMIT CCU mix clock driver, specifically in the ccu_mix_trigger_fc() function. An inverted condition causes the function to skip the frequency change trigger when it should execute, and vice versa. This breaks the dynamic frequency scaling subsystem (cpufreq), resulting in kernel panics during frequency transitions. The vulnerability is local in nature, requires user-level privileges to trigger (via standard cpufreq operations), and causes a denial of service through system instability.

Business impact

Organizations deploying Linux on SpaceMIT-based systems face unexpected kernel crashes during normal CPU frequency scaling operations, degrading system reliability and availability. This is particularly problematic in data centers, edge computing environments, or embedded systems relying on SpaceMIT processors where cpufreq scaling is used for power efficiency. Service interruptions and the need for immediate patching create operational overhead and potential SLA impacts.

Affected systems

Linux kernel versions running on SpaceMIT processor-based systems with the CCU mix clock driver active. The vulnerability specifically affects systems where cpufreq scaling is enabled or automatically triggered. Check your kernel version against the official Linux kernel advisory to determine if your system is vulnerable; SpaceMIT-based hardware includes select ARM-based embedded and mobile platforms.

Exploitability

The vulnerability requires local access and user-level privileges to trigger—an authenticated user can simply initiate CPU frequency scaling operations that are normal for power management, causing a kernel panic without any special exploit code. The condition is trivial to reach during routine system operation. No public exploit code is needed; the crash occurs through standard kernel APIs. The CVSS score of 5.5 (Medium) reflects the local requirement and privilege threshold, though the impact on system availability is severe.

Remediation

Apply the kernel patch that corrects the inverted condition in the ccu_mix_trigger_fc() function. The fix is straightforward: inverting the boolean logic to restore correct behavior. Verify the patched version through official Linux kernel repositories or your distribution's security advisories. Test the patch in a non-production environment first, particularly focusing on cpufreq scaling under load, before rolling out to production SpaceMIT-based systems.

Patch guidance

Obtain the corrected kernel version from your Linux distribution's security update channel or directly from kernel.org. The patch addresses only the inverted conditional logic and carries minimal risk of side effects. Apply during a maintenance window and verify cpufreq functionality post-reboot (check /sys/devices/system/cpu/cpu*/cpufreq/ for expected frequency scaling). Distributions shipping SpaceMIT kernel support should prioritize this update given the high impact on system stability.

Detection guidance

Monitor kernel logs for repeated panic messages correlating with cpufreq frequency transitions (look for stack traces mentioning ccu_mix_trigger_fc or clock driver failures). Systems experiencing random, undiagnosed kernel panics during normal operation—especially after idle periods when frequency scaling typically occurs—should be considered potentially vulnerable. Verify current kernel version against patched versions using 'uname -r' and cross-reference against official advisories. Proactive testing: attempt to trigger frequency scaling changes on test systems and observe for panic.

Why prioritize this

While the CVSS score is Medium (5.5), the practical impact on SpaceMIT-based deployments is high due to the reliability implications. The vulnerability is trivially reachable, requires no special privileges beyond user level, and directly impacts system uptime. Any SpaceMIT Linux deployment should prioritize patching to restore stability. Organizations using these systems for production workloads should treat this as high-priority; those in development or low-criticality roles can follow standard patching cycles.

Risk score, explained

CVSS 3.1 score of 5.5 reflects: local attack vector (user-level access required), low attack complexity (standard cpufreq operations), low privilege requirements (user context), no user interaction needed, unchanged scope, no confidentiality or integrity impact, but high availability impact (kernel panic). The score appropriately captures the severity of denial of service through instability, balanced against the requirement for local access. Real-world risk for SpaceMIT deployments is substantively higher due to frequency scaling being a routine, automatic operation.

Frequently asked questions