CVE-2018-20169 in Linux
Summary
by MITRE
An issue was discovered in the Linux kernel before 4.19.9. The USB subsystem mishandles size checks during the reading of an extra descriptor, related to __usb_get_extra_descriptor in drivers/usb/core/usb.c.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 06/19/2023
The vulnerability identified as CVE-2018-20169 represents a critical flaw within the Linux kernel's USB subsystem that existed prior to version 4.19.9. This issue stems from improper handling of size validation checks during the processing of USB extra descriptors, specifically within the __usb_get_extra_descriptor function located in the drivers/usb/core/usb.c file. The root cause of this vulnerability lies in the kernel's failure to adequately validate the size parameters when reading additional USB device configuration data, creating a potential pathway for malicious actors to exploit memory handling inconsistencies in the kernel's USB driver implementation.
The technical nature of this vulnerability places it squarely within the realm of buffer overflows and memory corruption issues, as defined by CWE-129 and CWE-787 categories. When the USB subsystem processes extra descriptors from connected devices, the insufficient size validation allows for potential manipulation of memory boundaries during descriptor parsing operations. This flaw enables attackers to craft specially crafted USB devices or manipulate existing USB communications in ways that can trigger memory corruption, potentially leading to privilege escalation or system instability. The vulnerability specifically affects the kernel's USB core functionality and can be exploited through malicious USB devices that present malformed extra descriptors during the enumeration process.
From an operational standpoint, this vulnerability presents significant security implications for Linux systems that support USB connectivity, as it can be exploited without requiring special privileges or user interaction. The attack surface is broad since any system with USB capabilities could be targeted, including desktop computers, servers, and embedded systems. The potential impact ranges from denial of service conditions that can crash the system to more severe exploitation scenarios where attackers might gain elevated privileges within the kernel space. This makes the vulnerability particularly dangerous in environments where USB devices are frequently connected or where systems are not properly secured against physical access attacks.
The mitigation strategy for CVE-2018-20169 primarily involves updating the Linux kernel to version 4.19.9 or later, which includes the necessary patches to address the size validation issue in the USB subsystem. System administrators should prioritize patching affected systems, particularly those in critical infrastructure environments where USB connectivity is prevalent. Additional protective measures include implementing USB device access controls through udev rules, disabling unnecessary USB ports when not in use, and monitoring USB device connections for suspicious activity. Organizations should also consider implementing USB device whitelisting policies and maintaining regular kernel updates to ensure protection against similar vulnerabilities. The remediation aligns with standard security practices outlined in the NIST Cybersecurity Framework and follows the principle of least privilege in USB device management as recommended by various security standards and best practices.