CVE-2016-3775 in Android
Summary
by MITRE
The kernel filesystem implementation in Android before 2016-07-05 on Nexus 5X, Nexus 6, Nexus 6P, Nexus Player, and Pixel C devices allows attackers to gain privileges via a crafted application, aka internal bug 28588279.
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Analysis
by VulDB Data Team • 02/22/2019
The vulnerability identified as CVE-2016-3775 represents a critical privilege escalation flaw within the Android kernel filesystem implementation that affected multiple high-profile devices including the Nexus 5X, Nexus 6, Nexus 6P, Nexus Player, and Pixel C. This weakness stems from improper validation of filesystem operations within the kernel space, creating an avenue for malicious applications to elevate their privileges from standard user-level access to system-level control. The vulnerability was particularly concerning as it exploited fundamental aspects of the operating system's security model, allowing attackers to bypass core security mechanisms that typically protect system integrity.
The technical nature of this flaw resides in the kernel's handling of filesystem operations where insufficient input validation permitted crafted applications to manipulate kernel data structures through carefully constructed filesystem calls. This vulnerability falls under the CWE category of improper input validation, specifically CWE-20, which addresses weaknesses in input validation that can lead to privilege escalation attacks. The implementation error occurred in the kernel filesystem subsystem where the system failed to properly verify the legitimacy of filesystem operations initiated by user-space applications, creating a pathway for attackers to exploit memory corruption vulnerabilities.
The operational impact of CVE-2016-3775 was severe as it enabled attackers to execute arbitrary code with kernel-level privileges, effectively compromising the entire device security model. Once exploited, the vulnerability allowed malicious applications to gain root access, enabling them to modify system files, install persistent backdoors, access all user data, and completely subvert the device's security protections. This type of privilege escalation attack directly aligns with ATT&CK technique T1068, which covers 'Local Privilege Escalation' and represents one of the most dangerous attack vectors in mobile security contexts.
The exploitation of this vulnerability required a crafted application that could trigger the specific kernel filesystem implementation flaw, typically through manipulation of filesystem operations such as symlink attacks or improper handling of file system metadata. Attackers could leverage this weakness to bypass the standard Android security model that normally separates user applications from system-level operations, effectively breaking the security boundaries that protect device integrity. The vulnerability was particularly dangerous because it affected devices that were considered flagship models, meaning that successful exploitation could compromise high-value targets with advanced security features and widespread usage.
Mitigation strategies for CVE-2016-3775 required immediate deployment of Android security patches released by Google, which addressed the kernel filesystem implementation flaws through proper input validation and enhanced kernel security checks. Organizations and users were advised to apply the July 2016 security updates promptly, as the vulnerability remained exploitable until patched. The recommended remediation approach aligned with standard security practices for kernel-level vulnerabilities, emphasizing the importance of timely patch management and the need for comprehensive security testing of kernel components. Additionally, security researchers recommended implementing application sandboxing measures and monitoring for suspicious filesystem operations to detect potential exploitation attempts, while also highlighting the critical need for ongoing kernel security audits to identify similar implementation flaws that could create similar privilege escalation pathways.