CVE-2025-68374 in Linux
Summary
by MITRE • 12/24/2025
In the Linux kernel, the following vulnerability has been resolved:
md: fix rcu protection in md_wakeup_thread
We attempted to use RCU to protect the pointer 'thread', but directly passed the value when calling md_wakeup_thread(). This means that the RCU pointer has been acquired before rcu_read_lock(), which renders rcu_read_lock() ineffective and could lead to a use-after-free.
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Analysis
by VulDB Data Team • 12/25/2025
The vulnerability CVE-2025-68374 represents a critical race condition and improper RCU (Read-Copy-Update) protection mechanism within the Linux kernel's md (Multiple Device) subsystem. This issue specifically affects the md_wakeup_thread function which manages asynchronous thread operations for software RAID configurations. The flaw demonstrates a fundamental misunderstanding of RCU synchronization primitives and their proper usage patterns within kernel space. The md subsystem is responsible for managing software RAID arrays and relies heavily on proper synchronization mechanisms to ensure data integrity and prevent memory safety issues during concurrent operations.
The technical root cause of this vulnerability stems from a violation of RCU ordering requirements where the kernel attempted to protect a pointer named 'thread' using RCU mechanisms but failed to maintain proper lock ordering. The implementation directly passed an RCU-protected pointer value to the md_wakeup_thread function without first acquiring the necessary rcu_read_lock() protection. This fundamental error creates a scenario where the RCU pointer is accessed before the appropriate read lock is acquired, effectively nullifying the protection mechanism. The improper ordering means that when the md_wakeup_thread function processes the thread pointer, it operates on potentially stale or freed memory references, creating a use-after-free condition that can be exploited by malicious actors.
The operational impact of this vulnerability extends beyond simple memory corruption, as it represents a potential path for privilege escalation and system instability within Linux environments utilizing software RAID configurations. When the md subsystem manages RAID arrays, particularly during array resync operations, rebuilds, or failover scenarios, the affected code path can be triggered through normal system operations or malicious input. The use-after-free condition could allow attackers to execute arbitrary code with kernel privileges, potentially leading to complete system compromise. This vulnerability particularly affects systems running kernel versions where the md subsystem is actively managing RAID arrays, making it relevant to enterprise servers, storage appliances, and any Linux system implementing software RAID functionality. The risk is amplified because the vulnerability exists in kernel space where successful exploitation can result in persistent system compromise and data loss.
Mitigation strategies for CVE-2025-68374 require immediate kernel updates to address the improper RCU protection implementation. System administrators should prioritize patching affected systems, particularly those running kernel versions containing the vulnerable md subsystem code. The fix involves correcting the RCU lock ordering by ensuring that rcu_read_lock() is acquired before accessing RCU-protected pointers, and subsequently releasing the lock appropriately after the function call completes. Additionally, organizations should conduct vulnerability assessments to identify systems running affected kernel versions and implement monitoring for unusual system behavior that might indicate exploitation attempts. Network segmentation and access controls should be maintained to limit potential attack surface, while regular system audits should verify proper patch application and monitor for any signs of compromise. This vulnerability aligns with CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization) and represents a specific implementation failure within the ATT&CK framework's privilege escalation techniques, particularly relevant to kernel-level exploits targeting storage subsystems.