CVE-2023-52898 in Linux
Summary
by MITRE • 08/21/2024
In the Linux kernel, the following vulnerability has been resolved:
xhci: Fix null pointer dereference when host dies
Make sure xhci_free_dev() and xhci_kill_endpoint_urbs() do not race and cause null pointer dereference when host suddenly dies.
Usb core may call xhci_free_dev() which frees the xhci->devs[slot_id]
virt device at the same time that xhci_kill_endpoint_urbs() tries to loop through all the device's endpoints, checking if there are any cancelled urbs left to give back.
hold the xhci spinlock while freeing the virt device
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Analysis
by VulDB Data Team • 02/17/2026
The vulnerability identified as CVE-2023-52898 represents a critical null pointer dereference issue within the Linux kernel's USB xHCI (eXtensible Host Controller Interface) driver implementation. This flaw occurs during the handling of USB host controller failures, specifically when the USB subsystem attempts to clean up device resources while the host controller experiences an unexpected shutdown. The root cause stems from a race condition between two critical kernel functions that manage USB device cleanup operations. The xhci_free_dev() function is responsible for freeing virtual device structures within the xHCI driver's internal data structures, while xhci_kill_endpoint_urbs() handles the cleanup of pending USB requests associated with device endpoints. When these functions execute concurrently during host failure scenarios, they create a timing window where one function may attempt to access memory that has already been freed by another, leading to the null pointer dereference condition.
The technical implementation of this vulnerability demonstrates a classic concurrency issue within kernel space USB device management. The xHCI driver maintains an array of virtual device structures indexed by slot_id within the xhci->devs[] array, which serves as the central repository for tracking active USB devices. During normal operation, when a USB host controller experiences a sudden failure, the kernel's USB core layer invokes cleanup routines to properly terminate device operations and release associated resources. However, the race condition occurs because xhci_free_dev() removes the virtual device entry from the xhci->devs[slot_id] array while xhci_kill_endpoint_urbs() may still be iterating through endpoint structures that reference the same device. This simultaneous access pattern creates a scenario where xhci_kill_endpoint_urbs() attempts to traverse endpoint lists that point to memory locations that have already been deallocated by xhci_free_dev(), resulting in the null pointer dereference that can cause system instability or potential privilege escalation.
The operational impact of this vulnerability extends beyond simple system crashes, as it represents a potential security risk within embedded systems and server environments where USB device management is critical. When the null pointer dereference occurs, it can lead to kernel panic conditions that require system reboot, disrupting service availability and potentially creating denial of service scenarios. The vulnerability is particularly concerning in environments where USB devices are frequently connected and disconnected or where USB host controllers may experience transient failures due to hardware issues or power management events. From an attacker perspective, this race condition could potentially be exploited to achieve privilege escalation or system compromise, especially in embedded systems or IoT devices where proper error handling and resource cleanup are essential for maintaining system integrity. The flaw affects systems running Linux kernel versions where the xHCI driver implementation has not received the specific fix addressing this race condition.
The mitigation strategy for CVE-2023-52898 involves implementing proper synchronization mechanisms within the xHCI driver to prevent concurrent access to virtual device structures during cleanup operations. The fix requires holding the xHCI spinlock during the execution of xhci_free_dev() to ensure exclusive access to the device structures while other cleanup functions are in progress. This approach aligns with established kernel development practices for handling concurrent access to shared resources and prevents the race condition that leads to null pointer dereference. The spinlock mechanism ensures that when one function is modifying or accessing the virtual device structures, no other function can simultaneously access the same memory locations, thereby eliminating the timing window that enables the race condition. This fix directly addresses the underlying CWE-362 weakness category related to concurrent access to shared resources without proper synchronization, and it follows ATT&CK technique T1068 by potentially enabling privilege escalation through kernel memory corruption. System administrators should ensure their Linux kernels are updated to versions containing this specific fix, particularly in environments where USB device reliability is critical, and where the vulnerability could be exploited to compromise system integrity or availability.