CVE-2016-3747 in Android
Summary
by MITRE
Use-after-free vulnerability in the mm-video-v4l2 venc component in mediaserver in Android 4.x before 4.4.4, 5.0.x before 5.0.2, 5.1.x before 5.1.1, and 6.x before 2016-07-01 allows attackers to gain privileges via a crafted application, as demonstrated by obtaining Signature or SignatureOrSystem access, aka internal bug 27903498.
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Analysis
by VulDB Data Team • 02/21/2019
The vulnerability described in CVE-2016-3747 represents a critical use-after-free flaw within the multimedia subsystem of Android operating systems, specifically affecting the mm-video-v4l2 venc component in the mediaserver process. This vulnerability exists in multiple Android versions including 4.x before 4.4.4, 5.0.x before 5.0.2, 5.1.x before 5.1.1, and 6.x before the specified date. The flaw occurs within the video encoding functionality of the Android media framework, where improper memory management allows attackers to manipulate freed memory locations and potentially execute arbitrary code with elevated privileges. The vulnerability is particularly concerning as it enables attackers to escalate privileges from regular application level access to system-level permissions, specifically targeting Signature or SignatureOrSystem access levels that provide extensive system control capabilities.
The technical exploitation of this use-after-free vulnerability involves the manipulation of memory allocation and deallocation patterns within the mediaserver process during video encoding operations. When the mm-video-v4l2 venc component processes multimedia data, it fails to properly validate or manage memory references, creating opportunities for attackers to craft malicious applications that trigger the freeing of memory blocks while still maintaining references to them. This memory corruption allows for potential code execution within the privileged mediaserver context, which operates with elevated system permissions. The vulnerability's classification under CWE-416 indicates improper deallocation of memory resources, while the privilege escalation aspect aligns with ATT&CK technique T1068 which involves exploiting legitimate credentials or privileges to gain higher-level access. The specific nature of the flaw enables attackers to leverage the mediaserver's elevated privileges to obtain system-level access that would normally require signature-level permissions.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it provides attackers with comprehensive control over affected Android devices. Successful exploitation allows adversaries to execute code with Signature or SignatureOrSystem privileges, which grants access to sensitive system functions, application signing keys, and potentially full device control. The mediaserver process is a critical component that handles multimedia operations across various applications, making this vulnerability particularly dangerous as it can be triggered through normal media processing activities. The timing of the vulnerability's exposure, particularly in Android versions released before the specified date, indicates that numerous devices in the field remained vulnerable for extended periods. This vulnerability directly affects the principle of least privilege by allowing unprivileged applications to gain system-level access, potentially enabling data exfiltration, persistent backdoor installation, and complete device compromise.
Mitigation strategies for CVE-2016-3747 primarily focus on updating affected Android systems to versions that contain patches for the memory management issues within the mm-video-v4l2 venc component. Organizations and users should prioritize immediate deployment of security updates released by Google and device manufacturers, as the vulnerability's exploitation can lead to complete device compromise. The patch implementations typically involve proper memory deallocation procedures and validation checks within the mediaserver process to prevent use-after-free conditions. Additionally, security monitoring should focus on detecting anomalous media processing activities that might indicate exploitation attempts, while application sandboxing and privilege separation can help limit potential damage even if exploitation occurs. Network-based detection measures can monitor for suspicious multimedia data processing patterns that might indicate attempts to trigger the vulnerability, though the most effective mitigation remains timely patch deployment. The vulnerability underscores the importance of secure coding practices in system-level components and highlights the need for comprehensive memory management validation in multimedia frameworks, particularly those handling user-provided data inputs.