CVE-2016-3940 in Android
Summary
by MITRE
The Synaptics touchscreen driver in Android before 2016-10-05 on Nexus 6P and Android One devices allows attackers to gain privileges via a crafted application, aka internal bug 30141991.
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Analysis
by VulDB Data Team • 05/01/2019
The vulnerability identified as CVE-2016-3940 represents a critical privilege escalation flaw within the Synaptics touchscreen driver component of Android operating systems. This weakness specifically affected devices including the Nexus 6P and Android One models, creating a pathway for malicious actors to elevate their system privileges through carefully constructed applications. The vulnerability stems from insufficient input validation and improper access controls within the driver's implementation, allowing unauthorized code execution with elevated privileges. The flaw was particularly concerning as it leveraged the touchscreen driver's privileged position within the Android security model, enabling attackers to bypass normal permission boundaries and gain root-level access to affected devices. This type of vulnerability falls under the CWE-20 category of "Improper Input Validation" and represents a classic example of how hardware driver components can serve as attack vectors for privilege escalation attacks. The vulnerability was documented internally as bug 30141991, highlighting the complexity of identifying and addressing such low-level system components.
The technical exploitation of CVE-2016-3940 occurs when a malicious application presents crafted input or commands to the Synaptics touchscreen driver that triggers an improper handling of privilege levels within the driver's code execution path. The vulnerability exploits the driver's failure to properly validate incoming data or commands, allowing an unprivileged application to manipulate the driver's behavior in ways that result in privilege elevation. This type of attack aligns with ATT&CK technique T1068 which describes "Exploitation for Privilege Escalation" and demonstrates how attackers can leverage driver-level vulnerabilities to gain system-level control. The flaw likely involves buffer overflows, improper access checks, or race conditions within the driver code that allow an attacker to execute arbitrary code with kernel-level privileges. The specific nature of the vulnerability means that attackers could potentially install malicious software, modify system files, or disable security features without proper authorization, fundamentally compromising the device's security posture.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it fundamentally undermines the security model of Android devices. Once exploited, attackers could gain complete control over affected devices, potentially leading to data theft, persistent backdoor installation, or the ability to monitor user activities. The vulnerability's presence on widely distributed devices like the Nexus 6P and Android One models meant that a substantial user base was potentially exposed to this risk. Organizations using these devices for sensitive operations would face significant security implications, as the vulnerability could be exploited remotely or through social engineering attacks that trick users into installing malicious applications. The impact is particularly severe given that touchscreen drivers typically operate with high privileges to ensure proper device functionality, creating a natural attack surface for privilege escalation. This vulnerability demonstrates how seemingly benign hardware components can become critical security risks when not properly secured against malicious input.
Mitigation strategies for CVE-2016-3940 primarily focus on patch management and system updates, as the vulnerability was addressed through official Android security updates released in October 2016. Device manufacturers and carriers should prioritize immediate deployment of security patches to affected devices, as the window for exploitation remains open until systems are properly updated. Users should ensure their devices receive and install all available security updates, particularly those addressing kernel-level drivers and system components. Network administrators should implement monitoring for suspicious application behavior that might indicate exploitation attempts, though detection of such attacks can be challenging given their sophisticated nature. The vulnerability highlights the importance of secure driver development practices and proper input validation, which should be enforced through security coding standards and regular code reviews. Organizations should also consider implementing application whitelisting policies to prevent installation of untrusted applications that could potentially exploit such vulnerabilities. Given the nature of the flaw, regular security assessments of device drivers and kernel components should be part of comprehensive security programs to identify and remediate similar vulnerabilities before they can be exploited by malicious actors.