CVE-2017-0861 in Communications LSMS
Summary
by MITRE
Use-after-free vulnerability in the snd_pcm_info function in the ALSA subsystem in the Linux kernel allows attackers to gain privileges via unspecified vectors.
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Analysis
by VulDB Data Team • 09/14/2025
The CVE-2017-0861 vulnerability represents a critical use-after-free flaw within the Advanced Linux Sound Architecture subsystem of the Linux kernel. This vulnerability specifically affects the snd_pcm_info function which is responsible for retrieving information about PCM (Pulse Code Modulation) audio devices. The issue arises from improper memory management where freed memory locations are accessed after being deallocated, creating potential exploitation opportunities for malicious actors. The vulnerability exists in the kernel's sound subsystem and can be triggered through specific audio device interactions that manipulate PCM device information structures. Such flaws are particularly dangerous because they can be exploited to escalate privileges from unprivileged users to root access, effectively compromising the entire system.
The technical implementation of this vulnerability stems from a classic memory safety issue where the snd_pcm_info function fails to properly validate or manage reference counts for allocated memory structures. When audio applications query PCM device information through the ALSA interface, the kernel allocates memory to store device metadata and configuration details. However, under certain conditions, the kernel does not properly handle the lifecycle of these memory allocations, leading to situations where freed memory blocks are still referenced or accessed by subsequent operations. This use-after-free condition creates a memory corruption scenario that can be leveraged by attackers to execute arbitrary code with elevated privileges. The vulnerability is particularly concerning because it operates at the kernel level where privilege escalation can result in complete system compromise.
The operational impact of CVE-2017-0861 extends beyond simple privilege escalation as it represents a fundamental security weakness that can be exploited across various Linux distributions and kernel versions. Attackers can leverage this vulnerability through malicious audio applications or by manipulating existing audio device interfaces to trigger the memory corruption condition. The exploitation typically involves crafting specific PCM device queries that cause the kernel to free memory structures while simultaneously allowing subsequent operations to reference those freed locations. This creates opportunities for attackers to inject malicious code into kernel memory space, potentially leading to complete system compromise. The vulnerability affects systems running affected kernel versions and can be particularly dangerous in server environments where audio services might be exposed to untrusted users or applications.
Mitigation strategies for CVE-2017-0861 primarily focus on immediate kernel updates and system hardening measures. The most effective approach involves applying the official kernel patches released by the Linux kernel security team, which address the memory management issues in the snd_pcm_info function. System administrators should prioritize updating their kernel versions to patched releases, typically kernel versions 4.11.8 or later for affected branches. Additionally, implementing proper access controls and limiting audio device access to trusted users can reduce exploitation surfaces. Network segmentation and monitoring for suspicious audio device access patterns can help detect potential exploitation attempts. From a security framework perspective, this vulnerability aligns with CWE-416 which describes use-after-free conditions, and represents a typical example of how kernel-level memory corruption can be leveraged for privilege escalation. The ATT&CK framework categorizes this under privilege escalation techniques where adversaries leverage kernel vulnerabilities to gain elevated system access, making it a critical concern for enterprise security teams managing Linux-based infrastructure.