CVE-2017-16645 in Linux
Summary
by MITRE
The ims_pcu_get_cdc_union_desc function in drivers/input/misc/ims-pcu.c in the Linux kernel through 4.13.11 allows local users to cause a denial of service (ims_pcu_parse_cdc_data out-of-bounds read and system crash) or possibly have unspecified other impact via a crafted USB device.
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Analysis
by VulDB Data Team • 01/06/2023
The vulnerability identified as CVE-2017-16645 resides within the Linux kernel's input subsystem, specifically in the ims-pcu driver component that handles communication with certain USB devices. This flaw manifests in the ims_pcu_get_cdc_union_desc function which processes USB communication descriptors for devices that implement the Communication Device Class Union descriptor format. The vulnerability represents a classic buffer over-read condition that occurs when the driver fails to properly validate input data from USB devices before processing it. The affected kernel versions range from the earliest releases through 4.13.11, indicating this issue has been present for several kernel cycles and affects a substantial portion of Linux systems that utilize USB input devices.
The technical implementation of this vulnerability stems from inadequate bounds checking within the USB descriptor parsing logic. When a maliciously crafted USB device connects to a system running an affected kernel version, the ims_pcu_parse_cdc_data function attempts to read data beyond the allocated buffer boundaries. This out-of-bounds read operation can result in kernel memory corruption, leading to system instability and potential crashes. The vulnerability is particularly concerning because it can be exploited through physical access or by connecting a malicious USB device, making it a significant attack vector for local privilege escalation or denial of service scenarios. The flaw demonstrates characteristics of CWE-129, which addresses improper validation of array indices, and CWE-787, which covers out-of-bounds write operations that can lead to memory corruption.
From an operational perspective, this vulnerability poses substantial risks to system availability and stability across various Linux distributions and embedded systems that rely on USB input device support. The denial of service impact can render systems unusable, particularly in environments where continuous operation is critical such as servers, industrial control systems, or embedded devices. The potential for unspecified other impacts suggests that in certain conditions, this vulnerability could potentially allow for more severe consequences including privilege escalation or information disclosure. Attackers could leverage this flaw by simply connecting a specially crafted USB device to a target system, making it an attractive vector for both casual attackers and more sophisticated threat actors who seek to disrupt system operations or establish persistent access points.
The exploitation of CVE-2017-16645 aligns with ATT&CK technique T1059 which covers execution through command and script interpreters, and more specifically relates to T1068 which addresses local privilege escalation. Organizations should prioritize patching affected systems with kernel updates that contain the fix for this vulnerability, as the mitigation is straightforward and involves upgrading to kernel versions that have addressed the buffer over-read condition. System administrators should also implement USB device whitelisting policies where possible, limiting the types of USB devices that can connect to critical systems. The vulnerability highlights the importance of robust input validation in kernel space drivers and demonstrates how seemingly minor flaws in device handling code can result in significant system stability issues. Regular kernel updates and security assessments of USB device drivers should be part of comprehensive cybersecurity strategies to prevent exploitation of similar vulnerabilities in the future.