CVE-2026-68092 in Linux
Summary
by MITRE • 08/10/2026
In the Linux kernel, the following vulnerability has been resolved:
time/jiffies: Register jiffies clocksource before usage
Teddy reported that a XEN HVM has a long boot delay, which was bisected to the recent enhancements to the negative motion detection. It turned out that the jiffies clocksource is used in early boot before it is registered, which leaves the max_delta_raw field at zero. That causes the read out to be clamped to the max delta of 0, which means time is not making progress.
Cure it by ensuring that it is initialized before its first usage in timekeeping_init().
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Analysis
by VulDB Data Team • 08/10/2026
This vulnerability represents a critical timing synchronization issue within the Linux kernel's time management subsystem that affects virtualized environments, particularly those using Xen HVM (Hardware Virtual Machine) configurations. The flaw occurs during the early boot process when the jiffies clocksource is accessed before it has been properly registered with the kernel's timekeeping framework. This premature usage creates a scenario where the max_delta_raw field remains uninitialized at zero, effectively preventing time progression and causing significant boot delays that can extend to several minutes in affected systems.
The technical root cause stems from improper initialization ordering within the timekeeping subsystem where the jiffies clocksource is referenced during early boot initialization before the timekeeping_init() function has completed its registration process. This creates a race condition where the clocksource's internal parameters are not properly configured, leading to a zero maximum delta value that clamps all time readings to zero. The vulnerability manifests specifically in Xen HVM environments due to their unique boot sequences and timing requirements, making it particularly problematic for virtualized workloads that depend on precise timekeeping.
From an operational perspective, this vulnerability directly impacts system availability and performance in virtualized environments, where extended boot times can cascade into service disruptions and resource allocation issues. The issue affects systems that rely on the jiffies clocksource for early time synchronization, which is critical for proper kernel initialization sequences and subsequent system operations. This vulnerability exposes systems to potential denial of service conditions during boot processes and can significantly impact automated deployment and scaling operations in cloud and virtualized infrastructures.
The mitigation strategy involves ensuring proper initialization ordering by registering the jiffies clocksource before its first usage within the timekeeping_init() function. This approach aligns with established kernel development practices for managing initialization dependencies and follows the principle of least privilege in resource allocation. The fix directly addresses the underlying race condition through proper sequencing of initialization steps, ensuring that all clocksource parameters are properly configured before they are accessed. This solution maintains backward compatibility while resolving the timing synchronization issue that affects virtualized environments and aligns with industry best practices for kernel time management.
The vulnerability demonstrates characteristics consistent with CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization) and relates to ATT&CK technique T1490 (Inhibit System Recovery) through its impact on system boot processes. This issue highlights the importance of proper initialization sequencing in kernel subsystems and underscores the need for comprehensive testing of early boot processes, particularly in virtualized environments where timing dependencies can become more complex. The fix represents a fundamental correction to the kernel's timekeeping initialization logic that prevents premature access to unregistered clocksources and ensures proper system boot progression across all supported virtualization platforms.