CVE-2022-50809 in Linux
Summary
by MITRE • 12/30/2025
In the Linux kernel, the following vulnerability has been resolved:
xhci: dbc: Fix memory leak in xhci_alloc_dbc()
If DbC is already in use, then the allocated memory for the xhci_dbc struct doesn't get freed before returning NULL, which leads to a memleak.
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Analysis
by VulDB Data Team • 01/01/2026
The vulnerability identified as CVE-2022-50809 represents a memory leak flaw within the Linux kernel's USB host controller driver subsystem, specifically affecting the xhci (eXtensible Host Controller Interface) implementation. This issue manifests in the xhci_alloc_dbc() function which manages the allocation of debug capability structures for USB host controllers. The problem occurs when the Debug Capability (DbC) functionality is already active within the system, creating a scenario where allocated memory resources for the xhci_dbc structure fail to be properly released before the function returns a NULL value. This memory management oversight directly violates fundamental principles of resource allocation and deallocation within kernel space operations, creating persistent memory consumption that can accumulate over time and potentially degrade system performance.
The technical flaw stems from improper error handling within the xhci driver's DbC allocation mechanism, where the function fails to implement proper cleanup procedures when encountering an already active DbC state. This represents a classic memory leak pattern that aligns with CWE-401, which categorizes memory leaks as a common weakness in software design where allocated memory is not properly deallocated. The root cause lies in the absence of conditional memory deallocation logic within the xhci_alloc_dbc() function, where developers failed to account for the scenario where DbC resources are already occupied and must be freed before returning NULL. This type of resource management error is particularly concerning in kernel space environments where memory exhaustion can lead to system instability or denial of service conditions, as the Linux kernel's memory management is critical for overall system operation.
The operational impact of this vulnerability extends beyond simple memory consumption, as it can contribute to progressive system degradation and potential service disruption. When multiple DbC allocation attempts occur in systems with active debug capabilities, the cumulative effect of unreleased memory structures can lead to memory exhaustion conditions that affect other kernel subsystems or user-space applications. The vulnerability is particularly concerning in embedded systems or server environments where continuous operation and resource efficiency are paramount. From an adversarial perspective, this memory leak could potentially be exploited as part of a denial of service attack, where an attacker repeatedly triggers DbC allocation attempts to consume available memory resources. The flaw also aligns with ATT&CK technique T1499.004, which involves resource exhaustion attacks that can be leveraged to disrupt system functionality.
Mitigation strategies for CVE-2022-50809 should focus on implementing proper resource cleanup mechanisms within the xhci driver code, ensuring that all allocated memory structures are appropriately deallocated regardless of the function's return path. System administrators should prioritize applying the relevant kernel patches that address this specific memory leak issue, as the fix typically involves adding conditional memory deallocation logic before the NULL return statement. Regular system monitoring should include memory usage tracking to detect potential accumulation of leaked memory structures, particularly in systems with active USB debugging capabilities. Additionally, organizations should implement comprehensive testing procedures for kernel updates to verify that memory management fixes are properly implemented and that no regressions have been introduced in USB host controller functionality. The resolution of this vulnerability demonstrates the importance of thorough error handling and resource management practices in kernel development, emphasizing the need for careful consideration of all code paths and their potential impact on system resources.