CVE-2023-54022 in Linux
Summary
by MITRE • 12/24/2025
In the Linux kernel, the following vulnerability has been resolved:
ALSA: usb-audio: Fix potential memory leaks at error path for UMP open
The allocation and initialization errors at alloc_midi_urbs() that is called at MIDI 2.0 / UMP device are supposed to be handled at the caller side by invoking free_midi_urbs(). However, free_midi_urbs() loops only for ep->num_urbs entries, and since ep->num_entries wasn't updated yet at the allocation / init error in alloc_midi_urbs(), this entry won't be released.
The intention of free_midi_urbs() is to release the whole elements, so change the loop size to NUM_URBS to scan over all elements for fixing the missed releases.
Also, the call of free_midi_urbs() is missing at snd_usb_midi_v2_open(). Although it'll be released later at reopen/close or disconnection, it's better to release immediately at the error path.
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Analysis
by VulDB Data Team • 12/26/2025
The vulnerability identified as CVE-2023-54022 represents a memory management flaw within the Linux kernel's Advanced Linux Sound Architecture ALSA subsystem, specifically affecting USB audio devices that implement MIDI 2.0/UMP (Universal MIDI Protocol) functionality. This issue resides in the usb-audio driver component that handles USB audio device communication and MIDI data processing. The flaw manifests during the initialization phase of MIDI 2.0/UMP devices when the system attempts to allocate and initialize USB MIDI Uniform Resource Block (URB) structures. The vulnerability stems from improper error handling mechanisms during resource allocation failures, creating a scenario where allocated memory resources are not properly released back to the system.
The technical root cause involves a mismatch between the loop iteration count used by the free_midi_urbs() function and the actual number of allocated URB elements. When alloc_midi_urbs() encounters allocation or initialization errors, it should trigger cleanup operations through free_midi_urbs() to release all allocated resources. However, the current implementation of free_midi_urbs() iterates based on ep->num_urbs which has not yet been updated to reflect the actual number of successfully allocated URBs at the error path. This discrepancy causes the function to miss releasing some allocated memory blocks, leading to memory leaks that persist until the device is disconnected or the system reboots. The problem specifically affects the USB MIDI 2.0/UMP device handling code path where the system attempts to establish communication with MIDI 2.0 capable USB audio devices.
The operational impact of this vulnerability extends beyond simple memory consumption issues to potentially affect system stability and performance over extended periods of operation. Memory leaks can accumulate over time, particularly in systems that frequently connect and disconnect USB MIDI devices or in environments where the ALSA subsystem handles numerous concurrent audio device connections. The vulnerability affects systems running Linux kernels that include the ALSA USB audio driver with MIDI 2.0/UMP support, making it relevant to audio workstations, professional music production environments, and any system utilizing USB MIDI devices. The delayed cleanup can result in progressive memory exhaustion, potentially leading to system slowdowns or even system crashes in extreme cases where memory resources become critically depleted.
The mitigation strategy for this vulnerability involves modifying the free_midi_urbs() function to iterate over the correct number of URB elements using NUM_URBS instead of ep->num_urbs, ensuring that all allocated resources are properly released regardless of where allocation errors occur during the initialization process. Additionally, the fix addresses the missing call to free_midi_urbs() within the snd_usb_midi_v2_open() function, ensuring immediate resource cleanup at error paths rather than relying on later cleanup operations during device disconnection or reconnection events. This fix aligns with common security practices for resource management and follows established patterns for error handling in kernel space programming. The vulnerability demonstrates characteristics consistent with CWE-401, which describes improper handling of memory allocation failures, and could potentially be leveraged by attackers to perform resource exhaustion attacks against systems running affected kernel versions. This issue is particularly relevant to the ATT&CK technique T1499.001, which covers resource exhaustion attacks, as it represents a potential vector for memory consumption attacks in systems with USB audio device support.