CVE-2013-1813 in BusyBox
Summary
by MITRE
util-linux/mdev.c in BusyBox before 1.21.0 uses 0777 permissions for parent directories when creating nested directories under /dev/, which allows local users to have unknown impact and attack vectors.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 12/27/2024
The vulnerability identified as CVE-2013-1813 resides within the BusyBox implementation of the mdev device manager utility, specifically in the util-linux/mdev.c component. This flaw manifests in the improper handling of directory permissions during the creation of nested directory structures under the /dev/ filesystem hierarchy. The issue affects BusyBox versions prior to 1.21.0, representing a significant security concern within embedded systems and minimal Linux environments where BusyBox serves as the primary set of Unix utilities.
The technical root cause of this vulnerability stems from the mdev utility's approach to directory creation, where it assigns overly permissive 0777 permissions to parent directories when establishing nested directory paths. This permission scheme grants read, write, and execute privileges to all users including the root user, which fundamentally compromises the security model of the /dev/ directory. The /dev/ filesystem serves as a critical component in Unix-like systems for device management, making it a prime target for privilege escalation attacks. The flaw occurs during the automatic device node creation process that happens when devices are detected and added to the system, typically through hotplug events or system initialization sequences.
The operational impact of this vulnerability extends beyond simple permission misconfiguration, creating potential attack vectors that could lead to system compromise. Local attackers with minimal privileges can exploit this weakness to manipulate the device node creation process, potentially leading to privilege escalation or denial of service conditions. The unknown impact and attack vectors mentioned in the CVE description reflect the complexity of how such permission flaws can be leveraged in various scenarios. An attacker could potentially create malicious device nodes with elevated permissions, manipulate existing device node permissions, or establish persistent access points through the compromised directory structure. This vulnerability particularly affects embedded systems, IoT devices, and minimal Linux installations where BusyBox is the standard utility suite and where the /dev/ directory hierarchy is frequently modified during system operation.
The security implications of this vulnerability align with CWE-276, which addresses incorrect permission assignment, and can be categorized under ATT&CK technique T1068, which involves the use of privilege escalation techniques through system configuration flaws. The vulnerability demonstrates how seemingly minor permission configuration errors can create significant security weaknesses in system utilities. Organizations using affected versions of BusyBox should implement immediate mitigation strategies including updating to BusyBox 1.21.0 or later, which contains the fix for this permission handling issue. Additional protective measures include implementing proper file system monitoring, reviewing directory permissions in the /dev/ hierarchy, and conducting comprehensive security assessments of embedded systems to identify other potential configuration flaws. The vulnerability underscores the importance of maintaining up-to-date system utilities and proper security hygiene in embedded environments where system resources are limited and security patches may not be applied as frequently as in enterprise systems.