CVE-2016-3875 in Android
Summary
by MITRE
server/wm/WindowManagerService.java in Android 6.x before 2016-09-01 does not enforce the DISALLOW_SAFE_BOOT setting, which allows physically proximate attackers to bypass intended access restrictions and boot to safe mode via unspecified vectors, aka internal bug 26251884.
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Analysis
by VulDB Data Team • 09/15/2022
The vulnerability described in CVE-2016-3875 represents a critical security flaw in Android 6.0 Marshmallow's WindowManagerService component that undermines the operating system's intended security controls. This issue affects Android versions 6.x prior to the 2016-09-01 security patch release, creating a significant backdoor that allows attackers with physical proximity to circumvent device security measures. The vulnerability specifically targets the DISALLOW_SAFE_BOOT setting, which is designed to prevent unauthorized access to safe mode boot configurations that could be exploited for malicious purposes. The flaw operates at the system level within the server/wm/WindowManagerService.java file, making it particularly dangerous as it resides in core operating system functionality that controls window management and user interface behavior.
The technical implementation of this vulnerability stems from a failure in the Android security framework's enforcement mechanisms. The DISALLOW_SAFE_BOOT setting is part of Android's device policy controls that should prevent users from entering safe mode, which is typically used for troubleshooting but can also serve as an attack vector for malware analysis or unauthorized system access. When this setting is not properly enforced, attackers can exploit unspecified vectors to gain access to safe mode boot processes without proper authentication or authorization. This represents a violation of the principle of least privilege and demonstrates a critical flaw in Android's security model where system-level protections are bypassed through physical access attacks. The vulnerability is categorized under CWE-284, which addresses improper access control, specifically the inadequate enforcement of access restrictions in system services. The attack vector requires only physical proximity to the device, making it particularly concerning for mobile devices that may be left unattended in public spaces or accessible to unauthorized individuals.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it enables attackers to bypass multiple layers of Android security controls that are designed to protect against unauthorized system modifications. Safe mode access typically provides a minimal environment that can be used to analyze or modify system behavior, and when accessible through this vulnerability, it creates opportunities for malware installation, system modification, or data extraction. The attack scenario allows adversaries to potentially access device encryption keys, modify system applications, or install persistent backdoors that could remain undetected for extended periods. This vulnerability particularly affects enterprise environments where Android devices may contain sensitive corporate data, as it enables attackers to circumvent device security policies that are meant to protect against unauthorized access. From an adversarial perspective, this flaw aligns with ATT&CK technique T1490, which covers 'Inhibit System Recovery' and represents a method of compromising system integrity by bypassing recovery mechanisms that are intended to prevent unauthorized access to system resources. The vulnerability also demonstrates the importance of physical security controls in mobile environments, where the attack surface expands beyond traditional network-based threats to include local physical access attacks.
The recommended mitigation strategies for this vulnerability primarily involve applying the security patches released by Google in the 2016-09-01 update cycle, which properly enforce the DISALLOW_SAFE_BOOT setting and address the underlying enforcement mechanism in WindowManagerService. Organizations should implement comprehensive device management policies that include regular security updates and ensure that all Android devices are running the latest security patches. Device administrators should also consider implementing additional security controls such as encryption enforcement, remote wipe capabilities, and restricted device policies that limit the ability to modify system configurations. For environments where physical security cannot be guaranteed, additional protective measures such as device encryption, secure boot processes, and regular security audits should be implemented to reduce the attack surface. The vulnerability highlights the importance of maintaining current security practices and demonstrates how seemingly minor implementation flaws in core system services can create significant security risks that affect millions of devices and potentially compromise sensitive information. Security teams should also consider implementing monitoring solutions that can detect unauthorized access attempts or system modifications that may indicate exploitation of this vulnerability.