CVE-2016-3887 in Android
Summary
by MITRE
providers/settings/SettingsProvider.java in Android 7.0 before 2016-09-01 does not properly enforce the DISALLOW_CONFIG_VPN setting, which allows attackers to bypass an intended always-on VPN state via a crafted application, aka internal bug 29899712.
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Analysis
by VulDB Data Team • 09/15/2022
The vulnerability described in CVE-2016-3887 represents a critical security flaw in Android 7.0's SettingsProvider implementation that undermines the operating system's VPN configuration controls. This issue specifically targets the DISALLOW_CONFIG_VPN restriction mechanism, which is designed to prevent unauthorized modification of VPN settings within corporate or restricted environments. The vulnerability allows malicious actors to circumvent intended security policies by exploiting a weakness in how the system validates VPN configuration permissions, potentially enabling unauthorized network traffic redirection and data interception.
The technical implementation flaw resides in the providers/settings/SettingsProvider.java file where the system fails to properly validate whether applications attempting to modify VPN settings have the necessary authorization. This weakness creates a path for attackers to craft malicious applications that can override the always-on VPN restriction, effectively bypassing the intended security controls. The vulnerability operates at the system level where the SettingsProvider component should enforce strict access controls but instead permits unauthorized modifications through crafted application behavior. This represents a failure in the principle of least privilege enforcement within Android's security architecture.
From an operational impact perspective, this vulnerability poses significant risks to enterprise security environments where always-on VPN configurations are critical for protecting sensitive data transmission. Organizations relying on Android 7.0 devices for corporate use may experience unauthorized network access, potential data exfiltration, and bypass of security monitoring systems. The vulnerability specifically affects devices running Android 7.0 before the 2016-09-01 security update, leaving millions of devices exposed to potential exploitation. Attackers could leverage this flaw to establish persistent network access points, conduct man-in-the-middle attacks, or redirect traffic through malicious VPN servers without user consent or awareness.
The vulnerability aligns with CWE-284 (Improper Access Control) and represents a failure in the Android security model's enforcement mechanisms. It also relates to ATT&CK technique T1071.004 (Application Layer Protocol: DNS) and T1021.002 (Remote Services: SMB/Windows Admin Shares) as attackers could potentially use the bypassed VPN functionality to redirect network traffic or establish unauthorized connections. Organizations should implement immediate mitigation strategies including applying the September 2016 security patches, reviewing VPN configuration policies, and monitoring for unauthorized VPN connection attempts. The vulnerability demonstrates the critical importance of proper access control implementation in mobile operating systems and highlights the need for comprehensive security testing of system-level components that govern network security policies.