CVE-2017-16643 in Linux
Summary
by MITRE
The parse_hid_report_descriptor function in drivers/input/tablet/gtco.c in the Linux kernel before 4.13.11 allows local users to cause a denial of service (out-of-bounds read and system crash) or possibly have unspecified other impact via a crafted USB device.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 01/06/2023
The vulnerability identified as CVE-2017-16643 resides within the Linux kernel's input subsystem, specifically in the gtco.c driver responsible for handling tablet devices. This flaw affects kernel versions prior to 4.13.11 and represents a critical security issue that can be exploited by local attackers through maliciously crafted USB devices. The vulnerability stems from improper input validation within the parse_hid_report_descriptor function, which processes Human Interface Device report descriptors from connected USB tablets. When a malformed HID report descriptor is received from a USB device, the kernel fails to properly bounds-check array accesses, leading to potentially exploitable memory access violations. The affected driver is part of the broader HID (Human Interface Device) subsystem that handles various input devices including graphics tablets, touchscreens, and other digitizers commonly used in professional and consumer environments. This issue is particularly concerning as it allows for privilege escalation from unprivileged local users to system-level control, potentially enabling complete system compromise.
The technical implementation of this vulnerability involves a classic out-of-bounds read condition that occurs during the parsing of HID report descriptors. When the parse_hid_report_descriptor function processes input from a USB tablet device, it does not adequately validate the length or structure of the incoming data, particularly in how it handles array indexing operations. The flaw manifests when the driver encounters a malformed report descriptor that specifies an invalid length or offset value, causing subsequent memory accesses to read beyond allocated buffer boundaries. This type of vulnerability is categorized as a buffer over-read according to CWE-125, which represents an improper restriction of operations within the bounds of a memory buffer. The vulnerability can be triggered simply by connecting a malicious USB device that presents a crafted HID report descriptor, making it particularly dangerous in environments where untrusted USB devices might be connected. The out-of-bounds read can result in kernel memory corruption, leading to system crashes, denial of service conditions, or potentially more severe exploitation scenarios. The attack vector is particularly insidious because it requires no special privileges beyond physical access to the system or the ability to connect a malicious USB device, making it a significant concern for both desktop and embedded systems.
The operational impact of CVE-2017-16643 extends beyond simple denial of service, as the vulnerability can potentially enable more sophisticated attacks depending on the execution environment and system configuration. A successful exploitation could allow an attacker to cause system crashes at will, effectively creating a persistent denial of service condition that could impact critical operations in industrial control systems, point-of-sale terminals, or other environments where tablet input devices are prevalent. The vulnerability also represents a potential pathway for privilege escalation, as the kernel memory corruption could theoretically be leveraged to execute arbitrary code with kernel privileges. In enterprise environments, this vulnerability poses significant risk to systems where USB devices are frequently connected, such as in shared workstations, kiosks, or public access terminals. The impact is particularly severe in embedded systems or IoT devices that rely on Linux kernel functionality and may not receive timely security updates. According to ATT&CK framework, this vulnerability could be classified under T1059 (Command and Scripting Interpreter) and T1068 (Exploitation for Privilege Escalation) as potential exploitation paths, though the initial access vector is through physical device connection rather than network-based attacks.
Mitigation strategies for CVE-2017-16643 primarily focus on applying the official kernel patch released with Linux kernel version 4.13.11, which addresses the bounds-checking issue in the parse_hid_report_descriptor function. System administrators should prioritize updating affected systems to kernel versions containing the fix, particularly in environments where USB device connectivity is not strictly controlled. Additional defensive measures include implementing USB device whitelisting policies that restrict which devices can connect to critical systems, disabling unnecessary USB ports or controllers, and employing kernel lockdown mechanisms that prevent loading of unsigned modules. Organizations should also consider implementing USB device monitoring solutions that can detect and alert on suspicious HID report descriptors or unusual device behavior. The vulnerability highlights the importance of proper input validation in kernel space code and demonstrates the critical need for thorough security testing of device drivers. Security teams should conduct vulnerability assessments to identify systems running vulnerable kernel versions and prioritize patching based on risk assessment of affected environments. Regular kernel updates and security monitoring are essential to prevent exploitation of similar vulnerabilities in the future, as this type of buffer over-read issue has been a recurring problem in kernel driver implementations. The fix implemented in kernel 4.13.11 demonstrates the effectiveness of proper bounds checking and input validation in preventing memory corruption vulnerabilities that could lead to system compromise.