CVE-2019-2131 in Android
Summary
by MITRE
An application with overlay permission can display overlays on top of settings UI. This could lead to local escalation of privilege with no additional execution privileges needed. User interaction is needed for exploitation. Product: Android. Versions: Android-7.0 Android-7.1.1 Android-7.1.2 Android-8.0 Android-8.1 Android-9. Android ID: A-119115683.
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Analysis
by VulDB Data Team • 08/01/2020
This vulnerability resides in the Android operating system's permission model and UI overlay mechanisms, specifically affecting versions from 7.0 through 9.0. The flaw allows applications that have been granted overlay permissions to display malicious overlays on top of the system settings interface, creating a critical security risk that can lead to local privilege escalation without requiring additional execution privileges. The vulnerability stems from insufficient validation of overlay permissions when displaying UI elements over system interfaces, enabling malicious applications to deceive users into granting elevated privileges or performing unauthorized actions. The attack requires user interaction, typically through a deceptive overlay that mimics legitimate system dialogs, making it particularly dangerous in social engineering scenarios where users might be tricked into confirming malicious actions.
The technical implementation of this vulnerability involves the Android system's WindowManager service and its handling of SYSTEM_ALERT_WINDOW permission. When an application with this permission attempts to display an overlay, the system should verify that the overlay does not interfere with critical system interfaces. However, the flaw allows these overlays to appear on top of the settings UI, potentially obscuring legitimate system prompts and creating opportunities for privilege escalation attacks. This weakness is categorized under CWE-284 Access Control Issues, specifically related to insufficient access control on system interfaces. The vulnerability demonstrates a failure in Android's security boundary enforcement, where the system fails to properly isolate system UI elements from potentially malicious overlays.
The operational impact of CVE-2019-2131 is significant as it enables attackers to exploit the trust users place in system interfaces. An attacker could craft a malicious overlay that appears to be a system settings prompt requesting additional permissions or asking for authentication credentials. This deception could lead to unauthorized privilege escalation, where the malicious application gains elevated system privileges or accesses sensitive user data. The vulnerability is particularly concerning because it operates within the legitimate Android permission model, making it difficult for users to detect malicious activity. From an attacker's perspective, this represents a low-effort, high-impact vector for privilege escalation that requires only the initial installation of a malicious application with overlay permissions and user interaction to complete the attack.
Mitigation strategies for this vulnerability involve both user education and system-level improvements. Users should be cautious when granting overlay permissions and should understand that applications with these permissions can display UI elements over system interfaces. Android security updates addressed this vulnerability by strengthening the validation of overlay permissions against system interfaces and implementing additional checks to prevent overlays from appearing over critical system UI elements. Organizations should ensure timely deployment of Android security patches and consider implementing mobile device management policies that restrict overlay permissions for sensitive applications. The vulnerability also highlights the importance of following ATT&CK framework principles, particularly in the area of privilege escalation techniques where adversaries might leverage system-level UI manipulation to gain elevated access. System administrators should monitor for applications requesting overlay permissions and implement security controls to prevent unauthorized applications from obtaining these capabilities.