CVE-2021-39617 in Android
Summary
by MITRE • 12/13/2022
In the user interface buttons of PermissionController, there is a possible way to bypass permissions dialogs due to a tapjacking/overlay attack. This could lead to local escalation of privilege with no additional execution privileges needed. User interaction is needed for exploitation.Product: AndroidVersions: Android-11 Android-12 Android-12LAndroid ID: A-175190844
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Analysis
by VulDB Data Team • 01/08/2023
The vulnerability identified as CVE-2021-39617 resides within the PermissionController component of Android operating systems version 11, 12, and 12L, representing a critical security flaw that exploits user interface overlay mechanisms to bypass permission dialogs. This vulnerability specifically targets the permission handling system where applications attempt to request user permissions for accessing sensitive resources or functionalities, creating an attack surface that malicious actors can leverage through sophisticated overlay techniques.
The technical flaw manifests through a tapjacking or overlay attack vector that allows malicious applications to position themselves over legitimate permission dialogs, effectively intercepting user interactions intended for the authentic permission interface. This occurs because the system fails to properly validate the authenticity of overlay elements that appear on top of permission prompts, creating an environment where attackers can manipulate user decisions without their knowledge or consent. The vulnerability operates at the user interface level where the system's permission dialog integrity is compromised through unauthorized overlay positioning, which can be achieved through carefully crafted malicious applications that exploit the trust relationship between the user interface and underlying permission handling mechanisms.
The operational impact of this vulnerability extends to potential local privilege escalation scenarios where attackers can gain elevated system privileges without requiring additional malicious code execution or root access. This represents a significant security risk as it allows adversaries to bypass the standard permission model that typically requires explicit user consent for accessing sensitive system resources. The attack requires only user interaction to be successful, making it particularly dangerous as it can be triggered through social engineering techniques or by exploiting user trust in familiar applications that may appear legitimate while actually being malicious.
From a cybersecurity perspective, this vulnerability aligns with CWE-693, which addresses protection mechanism failures related to user interface elements, and maps to ATT&CK technique T1068, which involves exploiting legitimate credentials and privileges to gain system access. The vulnerability represents a classic case of overlay attack exploitation where the attacker leverages the trust placed in user interface elements to manipulate system behavior. Security professionals should note that this vulnerability can be particularly challenging to detect as it operates within legitimate user interaction patterns and may not trigger traditional security monitoring systems that focus on code execution rather than user interface manipulation.
Mitigation strategies for this vulnerability should include implementing robust overlay detection mechanisms within the Android permission system, ensuring that only legitimate applications can position themselves over permission dialogs, and enhancing the user interface validation processes to detect and prevent unauthorized overlay positioning. System updates and patches from Google address this issue by strengthening the permission dialog integrity checks and implementing additional verification mechanisms for overlay elements. Organizations should prioritize immediate patch deployment and consider additional security measures such as monitoring for suspicious overlay behavior and implementing user education about the risks of interacting with unexpected UI elements during permission requests. The vulnerability highlights the importance of considering user interface security in mobile platforms and demonstrates how seemingly minor UI flaws can create significant privilege escalation opportunities for malicious actors.