CVE-2017-7874 in Linux
Summary
by MITRE
udevd in udev 232, when the Linux kernel 4.8.0 is used, does not properly verify the source of a Netlink message, which allows local users to execute arbitrary commands by leveraging access to the NETLINK_KOBJECT_UEVENT family, and the presence of the /lib/udev/rules.d/50-udev-default.rules file, to provide a crafted REMOVE_CMD value.
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Analysis
by VulDB Data Team • 12/27/2024
The vulnerability identified as CVE-2017-7874 represents a critical privilege escalation flaw within the udev daemon component of the Linux udev subsystem. This issue specifically affects udev version 232 when operating in conjunction with Linux kernel version 4.8.0, creating a dangerous condition where local attackers can execute arbitrary code with elevated privileges. The vulnerability stems from inadequate validation of Netlink message sources, which forms a fundamental security weakness in the system's device management infrastructure.
The technical flaw resides in the improper verification of source identification for Netlink messages within the udevd process. When the system receives a Netlink message through the NETLINK_KOBJECT_UEVENT family interface, the udev daemon fails to properly authenticate or validate the message origin. This allows malicious actors to craft and inject specially formatted messages that appear legitimate to the system. The vulnerability becomes exploitable when combined with the presence of the /lib/udev/rules.d/50-udev-default.rules file, which contains a crafted REMOVE_CMD value that can be manipulated by an attacker to execute arbitrary commands.
The operational impact of this vulnerability is severe and far-reaching, as it enables local privilege escalation from standard user accounts to root privileges. Attackers can leverage this flaw to gain complete system control without requiring physical access or additional authentication mechanisms. The exploit requires only local access to the system and the ability to send Netlink messages through the kernel interface. This makes the vulnerability particularly dangerous in multi-user environments or systems where local users might have limited access but could potentially escalate their privileges through this vector.
The security implications extend beyond simple privilege escalation, as this vulnerability can be exploited to bypass various system security controls and potentially compromise the entire system integrity. The flaw operates at a low system level within the udev subsystem, which is responsible for managing device nodes and handling device events in Linux systems. This makes the attack surface particularly broad as udev is involved in nearly all device management operations, including USB device handling, network interface management, and storage device operations. The vulnerability aligns with CWE-20, "Improper Input Validation," and can be mapped to ATT&CK technique T1068, "Local Privilege Escalation," through the exploitation of kernel-level components.
Mitigation strategies for this vulnerability include immediate patching of udev to versions that properly validate Netlink message sources and implement proper authentication mechanisms. System administrators should also consider implementing additional security controls such as restricting access to the NETLINK_KOBJECT_UEVENT family interface where possible, and monitoring for suspicious Netlink message patterns. The vulnerability highlights the importance of proper input validation and source authentication in kernel-level components, as well as the need for comprehensive security testing of system-level software components that handle inter-process communication mechanisms. Organizations should also implement regular security assessments of their udev configurations and monitor for unauthorized modifications to the default rules files that could facilitate exploitation of this and similar vulnerabilities.