CVE-2016-3923 in Android
Summary
by MITRE
The Accessibility services in Android 7.0 before 2016-10-01 mishandle motion events, which allows attackers to conduct touchjacking attacks and consequently gain privileges via a crafted application, aka internal bug 30647115.
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Analysis
by VulDB Data Team • 09/13/2025
The vulnerability identified as CVE-2016-3923 represents a critical security flaw in Android 7.0's accessibility services that was disclosed prior to the 2016-10-01 security patch release. This vulnerability stems from improper handling of motion events within the accessibility service framework, creating a fundamental weakness that attackers could exploit to manipulate user interactions on affected devices. The flaw specifically affects the Android operating system's accessibility features, which are designed to assist users with disabilities by providing alternative interaction methods. However, this particular vulnerability transforms these legitimate accessibility features into potential attack vectors.
The technical nature of this vulnerability resides in the way Android 7.0 processes motion events within its accessibility service implementation. When accessibility services receive motion events, the system fails to properly validate or sanitize these inputs, allowing malicious applications to inject crafted motion events that can be interpreted as legitimate user interactions. This creates a touchjacking scenario where an attacker's application can effectively hijack user touch input and redirect it to perform unauthorized actions. The vulnerability operates at the system level within the Android framework, specifically impacting the interaction between accessibility services and the input event processing pipeline. According to CWE classification, this represents a weakness in input validation and event handling mechanisms, specifically categorized under CWE-20: Improper Input Validation. The flaw allows for privilege escalation through indirect manipulation of the user interface, making it particularly dangerous as it can be exploited without requiring elevated privileges initially.
The operational impact of this vulnerability extends beyond simple touch manipulation, as it enables attackers to conduct sophisticated touchjacking attacks that can compromise user accounts, steal sensitive data, and perform unauthorized transactions. An attacker could craft a malicious application that appears benign to users while simultaneously exploiting this vulnerability to intercept and redirect touch events to target specific interface elements. This capability allows for the execution of unauthorized actions such as clicking on malicious links, entering credentials into fake interfaces, or performing financial transactions without user knowledge. The vulnerability's impact is particularly severe because it leverages legitimate system features that users often trust and enable for accessibility purposes. From an ATT&CK framework perspective, this vulnerability maps to multiple techniques including T1056.001: Input Injection and T1068: Exploitation for Privilege Escalation, as attackers can use the accessibility services to gain elevated privileges through indirect manipulation of system interactions.
Mitigation strategies for CVE-2016-3923 primarily involve applying the security patch released by Google in their October 2016 security update, which addressed the improper motion event handling within the accessibility services framework. Organizations and users should immediately update their Android devices to versions containing the patched accessibility service implementation. Additionally, security best practices recommend that users disable accessibility services when not actively needed, as these services can create additional attack surfaces. Network administrators should monitor for potential exploitation attempts and ensure that all Android devices within their environment are kept current with security patches. The vulnerability also highlights the importance of secure coding practices in system-level components, particularly in input handling and event processing within mobile operating systems. Regular security assessments of accessibility features and other system services should be conducted to identify potential similar vulnerabilities that could be exploited for privilege escalation or user interaction manipulation attacks.