CVE-2016-2187 in Linux
Summary
by MITRE
The gtco_probe function in drivers/input/tablet/gtco.c in the Linux kernel through 4.5.2 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 • 07/27/2022
The vulnerability identified as CVE-2016-2187 resides within the Linux kernel's input subsystem, specifically in the gtco_probe function located in drivers/input/tablet/gtco.c. This flaw affects Linux kernel versions through 4.5.2 and represents a critical security issue that can be exploited by attackers who are physically proximate to the target system. The vulnerability stems from inadequate input validation within the USB device descriptor processing logic, creating a pathway for maliciously crafted endpoint values to trigger system instability. The affected function processes USB tablet device descriptors and fails to properly validate endpoint configurations, leading to a scenario where malformed data can cause the kernel to attempt dereferencing a NULL pointer during device initialization.
The technical exploitation of this vulnerability occurs when a malicious USB device presents crafted endpoint values in its device descriptor that bypass normal validation checks. When the gtco_probe function processes these invalid endpoint configurations, it attempts to access memory locations that have not been properly initialized, resulting in a NULL pointer dereference. This type of error constitutes a classic kernel-level memory corruption vulnerability that can be leveraged to cause a system crash or complete denial of service. The vulnerability is particularly concerning because it requires only physical proximity to the target system, making it accessible through side-channel attacks or direct hardware manipulation. The flaw aligns with CWE-476 which describes NULL pointer dereference conditions, and represents a failure in input validation that can be categorized under the broader ATT&CK technique T1059.001 for command and scripting interpreter.
The operational impact of CVE-2016-2187 extends beyond simple system crashes, as it can be used to disrupt critical operations in environments where USB input devices are frequently connected or where system availability is paramount. Attackers can exploit this vulnerability to repeatedly crash systems, potentially leading to service disruption in enterprise environments or making devices unusable in embedded systems where physical access is possible. The vulnerability affects tablet input devices specifically, but the underlying issue demonstrates a broader pattern of inadequate input sanitization in kernel drivers that could potentially be exploited in other similar contexts. The fact that this vulnerability was present in kernel versions through 4.5.2 indicates a prolonged window of exposure, suggesting that organizations running older kernel versions may have been vulnerable for an extended period.
Mitigation strategies for CVE-2016-2187 primarily involve updating to patched kernel versions where the input validation has been strengthened to properly handle malformed endpoint values in USB device descriptors. System administrators should prioritize kernel updates, particularly for systems that may be exposed to untrusted USB devices or where physical proximity attacks are a concern. Additional protective measures include implementing USB device whitelisting policies, disabling unnecessary USB ports, and employing USB device authorization mechanisms that prevent unknown or untrusted devices from connecting to systems. Network segmentation and access controls can further reduce the attack surface by limiting physical access to critical systems. Organizations should also consider implementing monitoring solutions that can detect unusual system crashes or kernel panics that might indicate exploitation attempts. The vulnerability highlights the importance of robust input validation in kernel space and demonstrates the critical need for comprehensive security testing of device drivers, particularly those handling external hardware interfaces.