CVE-2019-2091 in Android
Summary
by MITRE
In GetPermittedAccessibilityServicesForUser of DevicePolicyManagerService.java, there is a possible permissions bypass due to a missing permission check. This could lead to local escalation of privilege, with no additional permissions required. User interaction is not needed for exploitation. Product: Android. Versions: Android-7.0 Android-7.1.1 Android-7.1.2 Android-8.0 Android-8.1. Android ID: A-128599660.
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Analysis
by VulDB Data Team • 06/21/2020
The vulnerability identified as CVE-2019-2091 resides within the Android operating system's DevicePolicyManagerService component, specifically in the GetPermittedAccessibilityServicesForUser method. This flaw represents a critical permission bypass issue that allows malicious applications to escalate their privileges locally without requiring any additional permissions. The vulnerability affects multiple Android versions including 7.0, 7.1.1, 7.1.2, 8.0, and 8.1, indicating a widespread impact across the Android ecosystem. The issue stems from a missing permission check within the device policy management service, which is responsible for controlling accessibility services and their associated permissions. This missing validation creates an exploitable path where unauthorized code can bypass normal permission boundaries and gain elevated privileges. The vulnerability's classification as a local privilege escalation means that an attacker who has already gained access to the device can leverage this flaw to elevate their privileges to that of system-level processes. This represents a significant security risk as it allows for complete system compromise without requiring user interaction, making it particularly dangerous in scenarios where malware might already be present on the device. The vulnerability's impact extends beyond simple privilege escalation, as it could potentially enable attackers to access sensitive system functions, modify critical device settings, or gain access to protected data that would normally be restricted to system applications. The flaw directly relates to CWE-284, which addresses improper access control issues in software systems. From an operational perspective, this vulnerability creates a pathway for attackers to bypass Android's security model that is designed to protect users from malicious applications. The attack surface is particularly concerning because it operates at the system level within the DevicePolicyManagerService, which is a core component of Android's security architecture. The missing permission check in GetPermittedAccessibilityServicesForUser essentially creates a backdoor that allows arbitrary code to access accessibility service permissions that should normally be restricted. This vulnerability's exploitation does not require any user interaction, which significantly increases its threat level and makes it particularly dangerous in automated attack scenarios. The Android ID A-128599660 assigned to this vulnerability indicates that it was properly tracked and addressed by Google's security team. The nature of this vulnerability suggests that it could be leveraged in conjunction with other exploits to create more sophisticated attack chains, potentially leading to complete device compromise. Organizations should note that this vulnerability represents a fundamental flaw in Android's permission model and could be used to undermine the entire security framework that protects Android devices from malicious applications. The impact of this vulnerability aligns with ATT&CK technique T1068, which involves exploiting vulnerabilities to gain elevated privileges, and T1059, which covers the use of system services for privilege escalation. The remediation of this vulnerability required updates to the Android operating system that properly enforced permission checks within the DevicePolicyManagerService, ensuring that only authorized components could access the accessibility service permissions. This case demonstrates the critical importance of proper permission validation in system-level services and highlights how a single missing permission check can create a pathway for complete system compromise. The vulnerability also underscores the need for comprehensive security testing of system services, particularly those that handle sensitive permissions and access controls. Security professionals should be aware that this vulnerability could have been used to bypass Android's security model entirely, allowing attackers to gain access to system-level functionality without proper authorization. The exploitation of such vulnerabilities demonstrates the ongoing challenge of maintaining secure operating system environments where a single flaw in core services can create widespread security implications. Organizations should prioritize updating affected Android devices to versions that contain patches for this vulnerability, as the risk of exploitation remains significant for unpatched systems. The vulnerability serves as a reminder of the critical role that device policy management plays in Android security and the potential consequences when these systems fail to properly enforce access controls.