CVE-2016-3689 in Linux
Summary
by MITRE
The ims_pcu_parse_cdc_data function in drivers/input/misc/ims-pcu.c in the Linux kernel before 4.5.1 allows physically proximate attackers to cause a denial of service (system crash) via a USB device without both a master and a slave interface.
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Analysis
by VulDB Data Team • 07/11/2022
The vulnerability identified as CVE-2016-3689 resides within the Linux kernel's input subsystem, specifically in the ims_pcu_parse_cdc_data function located in drivers/input/misc/ims-pcu.c. This flaw represents a classic buffer over-read condition that can be exploited by attackers who have physical proximity to a target system. The vulnerability affects Linux kernel versions prior to 4.5.1, making it a significant concern for systems that may be exposed to local physical access threats. The issue stems from improper validation of USB device configurations where the kernel fails to adequately check for the presence of both master and slave interfaces before processing incoming data.
The technical nature of this vulnerability can be categorized under CWE-129, which deals with insufficient validation of length of inputs to buffer operations. The ims_pcu_parse_cdc_data function processes data from USB devices that implement the USB Communication Device Class, specifically targeting devices that communicate through both master and slave interfaces. When a malicious USB device is connected that lacks both interfaces, the kernel's parsing logic attempts to access memory locations beyond the allocated buffer boundaries. This leads to memory corruption and ultimately results in a kernel panic that crashes the entire system. The vulnerability is particularly dangerous because it can be triggered through simple physical connection of a crafted USB device, requiring no network access or complex exploitation techniques.
From an operational impact perspective, this vulnerability presents a serious threat to systems where physical security is not adequately maintained. Attackers with physical access can easily exploit this weakness by connecting a specially crafted USB device that mimics the IMS PCU (Input/Output Management System Peripheral Control Unit) interface but omits one or both of the expected master and slave interface components. The denial of service impact is severe as it can cause complete system crashes, potentially leading to data loss, service interruption, and in critical infrastructure environments, operational downtime that could have significant financial and safety implications. This vulnerability aligns with ATT&CK technique T1059.001 for Command and Scripting Interpreter and T1133 for External Remote Services, as it can be exploited through physical access points to gain system control.
The mitigation strategy for CVE-2016-3689 involves upgrading to Linux kernel version 4.5.1 or later, which contains the necessary patches to properly validate USB device configurations before attempting to parse their data. System administrators should also implement USB device whitelisting policies and disable unnecessary USB interfaces where possible. Additional protective measures include enabling kernel lockdown modes, implementing USB guard mechanisms, and maintaining strict physical security controls around critical systems. The vulnerability demonstrates the importance of proper input validation in kernel space code and highlights how seemingly benign device enumeration processes can become attack vectors when proper boundary checks are not implemented. Organizations should conduct regular kernel updates and vulnerability assessments to ensure their systems remain protected against similar issues that may arise from improper device handling in kernel drivers.