CVE-2019-15927 in Linux
Summary
by MITRE
An issue was discovered in the Linux kernel before 4.20.2. An out-of-bounds access exists in the function build_audio_procunit in the file sound/usb/mixer.c.
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Analysis
by VulDB Data Team • 12/13/2023
The vulnerability identified as CVE-2019-15927 represents a critical out-of-bounds memory access flaw within the Linux kernel's USB audio subsystem. This issue affects kernel versions prior to 4.20.2 and specifically targets the build_audio_procunit function located in the sound/usb/mixer.c file. The flaw arises from insufficient input validation when processing USB audio device descriptors, creating a potential pathway for malicious actors to exploit memory corruption vulnerabilities. The affected component is part of the Linux audio subsystem that handles USB audio device communication, making it a significant concern for systems that rely on USB audio peripherals.
The technical nature of this vulnerability stems from improper bounds checking within the USB audio mixer processing logic. When the kernel attempts to parse audio device descriptors from USB audio devices, the build_audio_procunit function fails to validate array indices or buffer boundaries before accessing memory locations. This allows an attacker to craft specially formatted USB audio device descriptors that trigger memory access violations. The out-of-bounds access can result in kernel memory corruption, potentially leading to privilege escalation or system crashes. According to CWE-129, this vulnerability maps to improper input validation, while the ATT&CK framework would classify this under privilege escalation techniques through kernel exploits.
The operational impact of CVE-2019-15927 extends beyond simple system instability, as it creates opportunities for sophisticated attacks targeting the kernel's USB audio handling capabilities. Systems running affected kernel versions are vulnerable to malicious USB devices that could be used to execute arbitrary code with kernel privileges, potentially compromising the entire system. The vulnerability is particularly concerning in enterprise environments where USB audio devices are commonly used, including workstations, servers, and embedded systems. Attackers could leverage this flaw through physical access to devices or by tricking users into connecting malicious USB audio peripherals. The exploitability of this vulnerability increases the risk of persistent threats that could maintain system control even after reboot cycles.
Mitigation strategies for CVE-2019-15927 primarily focus on kernel version updates, with the most effective solution being the deployment of Linux kernel 4.20.2 or later. System administrators should prioritize patching affected systems and implementing automated update mechanisms to ensure timely deployment of security fixes. Additionally, organizations can implement USB device whitelisting policies to restrict which audio devices can connect to systems, reducing the attack surface. Network segmentation and monitoring solutions should be employed to detect anomalous USB device connections. The vulnerability highlights the importance of robust input validation in kernel space code and underscores the necessity of comprehensive security testing for device drivers. Organizations should also consider implementing kernel module signing and secure boot mechanisms to prevent exploitation of similar vulnerabilities in the future.