CVE-2016-3762 in Android
Summary
by MITRE
The sockets subsystem in Android 5.0.x before 5.0.2, 5.1.x before 5.1.1, and 6.x before 2016-07-01 allows attackers to gain privileges via a crafted application that uses (1) the AF_MSM_IPC socket class or (2) another socket class that is unrecognized by SELinux, aka internal bug 28612709.
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Analysis
by VulDB Data Team • 02/22/2019
The vulnerability described in CVE-2016-3762 represents a critical privilege escalation flaw within the Android operating system's socket subsystem that affected multiple versions including Android 5.0.x before 5.0.2, 5.1.x before 5.1.1, and 6.x before the 2016-07-01 security patch release. This issue stems from improper handling of socket classes within the Linux kernel's networking stack that Android utilizes for inter-process communication and system-level operations. The vulnerability specifically targets the AF_MSM_IPC socket class and other unrecognized socket classes that fail to be properly validated by the Security-Enhanced Linux (SELinux) framework, creating a pathway for malicious applications to bypass security controls and elevate their privileges.
The technical root cause of this vulnerability lies in the insufficient validation mechanisms within the socket creation and management processes. When applications attempt to create sockets using the AF_MSM_IPC class or other unrecognized socket types, the system fails to properly enforce SELinux policies that should normally restrict access based on application permissions and security contexts. This occurs because the kernel's socket subsystem does not adequately check whether the requesting process has proper authorization to use these specific socket classes, particularly when they are either proprietary or not explicitly defined in the standard socket class hierarchy. The vulnerability falls under CWE-264, which addresses permissions, privileges, and access controls, specifically in the context of improper access control mechanisms within kernel-level networking components.
The operational impact of this vulnerability is severe as it allows a malicious application to escalate privileges from a standard user-level process to a system-level privileged process without proper authorization. Attackers can exploit this weakness by crafting a malicious application that creates sockets using the vulnerable socket classes, thereby bypassing the normal security boundaries that should prevent unauthorized access to system resources. This privilege escalation capability enables attackers to gain access to sensitive system functions, read/write to protected memory areas, modify system configurations, and potentially access confidential data that would normally be restricted to system processes or privileged applications. The vulnerability essentially creates a backdoor mechanism that allows unprivileged applications to assume the security context and capabilities of system-level processes.
The attack vector for this vulnerability requires a malicious application to be installed on the target device, as the exploitation relies on the application's ability to create specific socket types. The attack does not require physical access or special privileges beyond what a standard application might normally have, making it particularly dangerous in environments where users can install third-party applications. This aligns with ATT&CK technique T1068, which covers "Local Privilege Escalation" through the exploitation of system-level vulnerabilities. The vulnerability demonstrates a failure in the principle of least privilege enforcement within the Android security model, where applications should not be able to access system resources that exceed their declared permissions and security contexts.
Mitigation strategies for this vulnerability primarily involve applying the security patches released by Google as part of their regular security updates for Android. Organizations and users should ensure that all Android devices are updated to versions that include the fix for this vulnerability, specifically Android 5.0.2, 5.1.1, and the corresponding 2016-07-01 security patches for Android 6.0. Additionally, system administrators should implement strict application installation policies that limit the ability of users to install applications from untrusted sources. Network monitoring solutions should be configured to detect unusual socket creation patterns that might indicate exploitation attempts. The fix implemented by Google addresses the core issue by strengthening the SELinux policy enforcement for socket classes and ensuring that unrecognized socket types are properly validated before granting access to system resources. This vulnerability highlights the importance of maintaining up-to-date security patches and the critical need for proper kernel-level access control mechanisms in mobile operating systems.