CVE-2016-2420 in Android
Summary
by MITRE
rootdir/init.rc in Android 4.x before 4.4.4 does not ensure that the /data/tombstones directory exists for the Debuggerd component, which allows attackers to gain privileges via a crafted application, aka internal bug 26403620.
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Analysis
by VulDB Data Team • 02/03/2019
The vulnerability identified as CVE-2016-2420 resides within the Android operating system's initialization process, specifically in the rootdir/init.rc file that governs system component setup. This flaw affects Android versions 4.x prior to 4.4.4 and represents a critical privilege escalation vulnerability that exploits the improper handling of directory creation during system boot. The issue manifests when the Debuggerd component, which is responsible for managing application crashes and debugging information, fails to verify the existence of the /data/tombstones directory before attempting to utilize it. This directory serves as a crucial storage location for crash dump information and debugging data generated by applications that encounter errors or are terminated unexpectedly. The absence of proper directory validation during the system initialization phase creates a security gap that malicious applications can exploit to elevate their privileges beyond normal user limitations.
The technical exploitation of this vulnerability occurs through a crafted application that deliberately attempts to access or manipulate the Debuggerd component's functionality. When the system initializes and processes the init.rc configuration, it fails to ensure that the /data/tombstones directory is properly created with appropriate permissions before the Debuggerd service begins operation. This oversight allows an attacker-controlled application to manipulate the directory creation process or to create a symbolic link pointing to a privileged location, thereby enabling the execution of arbitrary code with elevated privileges. The vulnerability directly relates to CWE-276, which addresses improper permissions for critical resources, and demonstrates how inadequate access control mechanisms during system initialization can compromise the entire security architecture. The flaw operates at the system level rather than at the application level, making it particularly dangerous as it can be leveraged to bypass standard Android security boundaries and gain root access to the device.
The operational impact of CVE-2016-2420 extends beyond simple privilege escalation, as it provides attackers with a pathway to completely compromise Android devices running vulnerable versions. Once an attacker successfully exploits this vulnerability, they can execute arbitrary code with root privileges, potentially gaining access to all device data, installing malicious applications, modifying system files, and even disabling security features. This type of vulnerability is particularly concerning in enterprise environments where Android devices may be used for sensitive data processing or as part of larger security infrastructures. The vulnerability's classification under the ATT&CK framework would align with techniques involving privilege escalation and persistence mechanisms, as attackers could establish persistent access to compromised devices. The impact is further amplified by the fact that this vulnerability affects devices that were widely deployed, meaning millions of users could be at risk. The flaw essentially undermines the fundamental security model of Android, which relies on proper initialization and access control to maintain system integrity.
Mitigation strategies for CVE-2016-2420 primarily focus on updating to patched Android versions, specifically Android 4.4.4 and later, which address the improper directory creation logic in the init.rc file. System administrators and device manufacturers should implement immediate patch deployment to protect affected devices from exploitation. Additionally, organizations should consider implementing network-level monitoring to detect suspicious activities that might indicate exploitation attempts, such as unusual access patterns to system directories or unexpected privilege escalation events. The vulnerability serves as a reminder of the importance of proper security practices during system initialization and highlights the necessity of comprehensive security testing for critical system components. Device manufacturers should also consider implementing runtime checks and validation mechanisms that can detect and prevent similar issues in future system configurations. Security teams should conduct regular audits of system initialization scripts and configurations to identify potential security gaps that could be exploited by adversaries. The remediation process should also include educating users about the importance of keeping their devices updated and avoiding installation of untrusted applications that might exploit such vulnerabilities.