CVE-2016-2186 in Linux
Summary
by MITRE
The powermate_probe function in drivers/input/misc/powermate.c in the Linux kernel before 4.5.1 allows physically proximate attackers to cause a denial of service (NULL pointer dereference and system crash) via a crafted endpoints value in a USB device descriptor.
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Analysis
by VulDB Data Team • 07/10/2022
The vulnerability identified as CVE-2016-2186 resides within the Linux kernel's input subsystem, specifically in the powermate_probe function located in drivers/input/misc/powermate.c. This flaw represents a classic null pointer dereference issue that can be exploited by attackers who have physical proximity to the target system. The vulnerability affects Linux kernel versions prior to 4.5.1, making it a significant concern for systems running older kernel versions where patching may not have been applied. The issue stems from inadequate input validation within the USB device descriptor processing logic, particularly when handling endpoint configurations.
The technical exploitation of this vulnerability occurs when a malicious USB device presents a crafted endpoints value in its device descriptor that triggers a NULL pointer dereference within the powermate_probe function. This function is responsible for probing and initializing USB input devices that use the PowerMate protocol, commonly found in audio and multimedia control devices. When the kernel processes a malformed USB descriptor containing invalid endpoint information, the powermate_probe function fails to properly validate the endpoint data structure before attempting to dereference pointers that may be NULL. This leads to an immediate system crash and denial of service condition, effectively rendering the affected system unusable until a reboot occurs.
From an operational perspective, the impact of CVE-2016-2186 is particularly concerning because it requires only physical proximity to exploit, making it a significant risk in environments where untrusted USB devices might be connected to systems. The vulnerability can be leveraged by attackers to perform persistent denial of service attacks against critical systems, potentially causing operational disruptions in enterprise environments, industrial control systems, or any infrastructure where system availability is paramount. The attack vector is particularly dangerous because USB devices are commonly used for legitimate purposes and are often trusted by users and systems, making this attack difficult to detect and prevent through traditional network-based security measures.
This vulnerability maps directly to CWE-476 which describes NULL Pointer Dereference, and aligns with several ATT&CK techniques including T1059 for system commands and T1499 for endpoint denial of service. The attack surface is particularly relevant for environments with USB device management policies that may not adequately validate device descriptors or for systems that automatically accept USB connections without proper device verification. Organizations should prioritize patching to kernel version 4.5.1 or later to address this vulnerability, as the fix involves proper validation of endpoint values in USB device descriptors before attempting to access them. Additionally, implementing USB device whitelisting policies and disabling unnecessary USB ports can provide additional defense-in-depth measures against this specific class of attack.