CVE-2011-0640 in udev
Summary
by MITRE
The default configuration of udev on Linux does not warn the user before enabling additional Human Interface Device (HID) functionality over USB, which allows user-assisted attackers to execute arbitrary programs via crafted USB data, as demonstrated by keyboard and mouse data sent by malware on a smartphone that the user connected to the computer.
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Analysis
by VulDB Data Team • 02/08/2019
The vulnerability described in CVE-2011-0640 represents a critical security flaw in the default udev configuration on Linux systems that fundamentally undermines user awareness and system integrity. This issue stems from the improper handling of Human Interface Device (HID) functionality within the USB subsystem, where the system automatically enables additional HID capabilities without alerting users to the potential risks involved. The vulnerability operates through a user-assisted attack vector where malicious actors can craft specific USB data payloads that trigger unintended system behavior when connected to vulnerable Linux machines. The attack scenario typically involves malware-infected smartphones or USB devices that, when connected to a computer, can automatically execute arbitrary programs through the HID functionality that udev has enabled without user consent or awareness.
The technical implementation of this vulnerability relies on the udev daemon's default behavior of automatically processing and enabling HID devices upon connection, without providing appropriate warnings or user confirmation mechanisms. When a USB HID device such as a keyboard or mouse is connected, udev automatically configures the device to operate at a higher privilege level, potentially allowing malicious code embedded in the device's firmware or data to execute with elevated privileges. This flaw falls under the category of insufficient user awareness and privilege escalation, with specific implications for the CWE-664 category of "Use of Potentially Dangerous Function" and CWE-707 category of "Improper Neutralization of Special Elements in Output Used by a Downstream Component." The vulnerability demonstrates how default security configurations can create dangerous attack surfaces when system administrators fail to properly configure security policies for device handling and user interaction.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass complete system compromise through what is essentially a man-in-the-middle attack on USB device connections. Attackers can exploit this flaw by creating malicious USB devices that, when connected to a vulnerable Linux system, automatically trigger the execution of malicious payloads through HID functionality. The attack requires user interaction in the form of device connection, but the system's lack of warning mechanisms means users remain unaware of the potential security implications. This vulnerability specifically aligns with ATT&CK technique T1210 "Exploitation of Remote Services" and T1059 "Command and Scripting Interpreter" as it allows attackers to execute arbitrary code through legitimate system interfaces. The implications for enterprise environments are particularly severe as users may unknowingly connect compromised devices, potentially leading to complete system compromise, data exfiltration, or lateral movement within networked environments.
Mitigation strategies for CVE-2011-0640 should focus on implementing proper udev rules and configuration policies that require explicit user confirmation before enabling HID functionality. System administrators should modify udev configuration files to disable automatic HID device activation or implement custom rules that warn users before device functionality is enabled. The solution involves configuring udev rules to require manual intervention or explicit user consent when HID devices are connected, effectively preventing the automatic privilege escalation that occurs in default configurations. Additionally, organizations should implement USB device whitelisting policies and consider disabling unnecessary HID device support in non-essential systems. The vulnerability highlights the importance of secure default configurations and demonstrates how seemingly benign device management features can create significant security risks when not properly secured. Organizations should also consider implementing network segmentation and endpoint detection measures to monitor for suspicious USB device connections and potential exploitation attempts.