CVE-2016-2496 in Android
Summary
by MITRE
The Framework UI permission-dialog implementation in Android 6.x before 2016-06-01 allows attackers to conduct tapjacking attacks and access arbitrary private-storage files by creating a partially overlapping window, aka internal bug 26677796.
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Analysis
by VulDB Data Team • 01/18/2019
The vulnerability identified as CVE-2016-2496 represents a critical security flaw in the Android framework's user interface permission dialog implementation affecting Android 6.x versions released before June 1, 2016. This issue stems from inadequate window management and overlay protection mechanisms that fail to properly validate the legitimacy of overlapping windows presented to users during permission requests. The flaw enables malicious actors to exploit the permission dialog system through carefully crafted overlay windows that appear to be legitimate system prompts while actually concealing malicious intent.
The technical exploitation of this vulnerability relies on the ability of attackers to create partially overlapping windows that can manipulate user interactions and deceive users into granting permissions to malicious applications. This tapjacking attack vector specifically targets the permission dialog interface where users expect to see genuine system prompts. The vulnerability operates by leveraging the Android windowing system's insufficient validation of window z-order and transparency properties, allowing attackers to position malicious windows over legitimate permission dialogs. This creates a scenario where users may unknowingly interact with malicious overlays while believing they are interacting with legitimate system interfaces, effectively bypassing the intended permission verification process.
The operational impact of CVE-2016-2496 extends beyond simple permission manipulation to encompass potential unauthorized access to private application storage and sensitive user data. When attackers successfully execute this attack, they can gain access to private storage files that would normally be protected by Android's permission model, including personal documents, photos, and application-specific data. This vulnerability particularly affects the Android 6.0 marshmallow release and earlier versions of the platform, representing a significant regression in the security model that was designed to protect user privacy and data integrity. The flaw directly violates the principle of least privilege and can lead to complete compromise of user application data and potentially system-level access depending on the targeted applications and their permissions.
This vulnerability maps to CWE-691, which specifically addresses insufficient protection of overlay windows in graphical user interfaces, and aligns with ATT&CK technique T1056.001 for input injection through UI manipulation. The attack vector specifically targets the Android framework's window management system and permission dialog implementation, creating a pathway for privilege escalation through user deception rather than direct system exploitation. Mitigation strategies include updating to Android 6.0.1 or later versions where Google patched the vulnerability through enhanced window validation mechanisms and improved overlay protection. Additionally, users should exercise caution when interacting with permission prompts and ensure they are using updated applications that properly implement Android security best practices. The fix implemented by Google involved strengthening the validation of window properties during permission dialog display and implementing more robust checks to prevent malicious overlay windows from appearing in legitimate permission contexts. Organizations should also implement mobile device management policies that enforce timely security updates and monitor for suspicious overlay behavior in enterprise environments.