CVE-2014-4652 in Linux
Summary
by MITRE
Race condition in the tlv handler functionality in the snd_ctl_elem_user_tlv function in sound/core/control.c in the ALSA control implementation in the Linux kernel before 3.15.2 allows local users to obtain sensitive information from kernel memory by leveraging /dev/snd/controlCX access.
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Analysis
by VulDB Data Team • 02/08/2022
The vulnerability identified as CVE-2014-4652 represents a critical race condition flaw within the Advanced Linux Sound Architecture (ALSA) subsystem of the Linux kernel. This issue specifically affects the snd_ctl_elem_user_tlv function located in sound/core/control.c, which handles user-space control elements and their associated TLV (Type-Length-Value) data structures. The flaw exists in kernel versions prior to 3.15.2 and creates a security exposure that can be exploited by local users with access to /dev/snd/controlCX devices, which are typically accessible to users in the audio group or with appropriate privileges. The race condition manifests when multiple threads or processes attempt to access the same TLV handler functionality simultaneously, creating a window where kernel memory contents can be inadvertently exposed to user-space applications.
The technical implementation of this vulnerability stems from improper synchronization mechanisms within the ALSA control subsystem's TLV handling code. When a user-space application interacts with the sound control interface through /dev/snd/controlCX devices, the kernel's snd_ctl_elem_user_tlv function processes TLV data structures that contain metadata about audio control elements. The race condition occurs during the processing of these TLV operations where the kernel fails to properly lock or synchronize access to shared memory regions containing sensitive kernel data. This allows an attacker to potentially read kernel memory contents through carefully crafted TLV operations, as the timing window created by concurrent access enables the exposure of information that should remain protected within kernel space.
From an operational perspective, this vulnerability presents significant risks to systems running affected kernel versions, particularly those with audio capabilities or applications that utilize ALSA interfaces. Local users who can access audio control devices can leverage this flaw to extract sensitive information from kernel memory, potentially including cryptographic keys, passwords, or other confidential data stored in kernel memory regions. The impact extends beyond simple information disclosure, as this vulnerability can serve as a stepping stone for more sophisticated attacks, allowing adversaries to gather intelligence about the system's memory layout and kernel structures. The vulnerability is particularly concerning in multi-user environments where audio device access is granted to non-privileged users, as it provides a means for privilege escalation or information gathering without requiring elevated privileges.
The exploitation of CVE-2014-4652 aligns with several ATT&CK framework techniques including T1003 (OS Credential Dumping) and T1059 (Command and Scripting Interpreter) where attackers might use the information disclosure to gain insights about system internals. From a CWE perspective, this vulnerability maps to CWE-362 which describes a race condition error, and CWE-200 which covers exposure of sensitive information. The vulnerability also relates to CWE-284 which addresses improper access control, as the flaw allows unauthorized access to kernel memory through legitimate device interfaces. Mitigation strategies include updating to kernel versions 3.15.2 or later where the race condition has been addressed through proper synchronization mechanisms. Additionally, system administrators should consider restricting access to audio control devices through appropriate permissions and group memberships, though the most effective solution remains applying the kernel security patch that resolves the underlying race condition in the ALSA subsystem's TLV handling implementation.