CVE-2014-4654 in Linux
Summary
by MITRE
The snd_ctl_elem_add function in sound/core/control.c in the ALSA control implementation in the Linux kernel before 3.15.2 does not check authorization for SNDRV_CTL_IOCTL_ELEM_REPLACE commands, which allows local users to remove kernel controls and cause a denial of service (use-after-free and system crash) by leveraging /dev/snd/controlCX access for an ioctl call.
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Analysis
by VulDB Data Team • 01/18/2022
The vulnerability identified as CVE-2014-4654 represents a critical authorization flaw within the Advanced Linux Sound Architecture (ALSA) subsystem of the Linux kernel. This issue exists in the snd_ctl_elem_add function located in sound/core/control.c, where the kernel fails to properly validate permissions when processing SNDRV_CTL_IOCTL_ELEM_REPLACE commands. The flaw specifically affects Linux kernel versions prior to 3.15.2, creating a persistent security weakness that has significant implications for system stability and integrity. The vulnerability stems from inadequate access control mechanisms that should have prevented unauthorized modifications to kernel sound controls.
The technical exploitation of this vulnerability occurs through the manipulation of /dev/snd/controlCX device files, which provide user-space applications with access to kernel-level sound control interfaces. When a local attacker executes an ioctl call with the SNDRV_CTL_IOCTL_ELEM_REPLACE command, the kernel's insufficient authorization checks allow the malicious operation to proceed without proper validation. This authorization bypass enables attackers to remove existing kernel controls, creating a use-after-free condition where freed memory locations are subsequently accessed by the kernel's sound subsystem. The improper handling of these control elements leads to memory corruption and ultimately results in system crashes or complete system hangs.
The operational impact of this vulnerability extends beyond simple denial of service, as it represents a fundamental breakdown in kernel security boundaries. Local users who can access the sound control device files can leverage this flaw to compromise system stability and potentially disrupt audio functionality for all running applications. The use-after-free condition created by removing kernel controls can lead to unpredictable behavior including kernel panics, system lockups, and in some cases, the possibility of privilege escalation. This vulnerability particularly affects systems running older kernel versions where the authorization checks were not properly implemented, making it a significant concern for enterprise environments and embedded systems relying on legacy kernel versions.
Mitigation strategies for CVE-2014-4654 focus primarily on kernel version updates, as the vulnerability was addressed through proper authorization checks implemented in kernel version 3.15.2. System administrators should prioritize upgrading to kernel versions 3.15.2 or later to eliminate this vulnerability. Additionally, access controls should be implemented to restrict unauthorized access to /dev/snd/controlCX device files, though this represents a partial mitigation since the vulnerability lies within the kernel's authorization mechanisms. The flaw aligns with CWE-284, which describes improper access control vulnerabilities, and could potentially be leveraged in conjunction with other attack vectors to achieve more severe outcomes within the ATT&CK framework, particularly under the privilege escalation and defense evasion categories. Organizations should also implement monitoring for unauthorized ioctl operations on sound control devices as part of their overall security posture to detect potential exploitation attempts.