CVE-2016-3746 in Android
Summary
by MITRE
Use-after-free vulnerability in the mm-video-v4l2 vdec 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 27890802.
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Analysis
by VulDB Data Team • 02/21/2019
The CVE-2016-3746 vulnerability represents a critical use-after-free flaw within the multimedia subsystem of Android operating systems, specifically affecting the mm-video-v4l2 vdec component in the mediaserver process. This vulnerability exists in Android versions 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 2016-07-01 security patch release. The flaw resides in the video decoding functionality that handles multimedia processing within the Android framework, making it particularly dangerous as it directly impacts the core media processing capabilities that numerous applications depend upon for video playback and encoding operations.
The technical nature of this vulnerability stems from improper memory management within the video decoder component where freed memory blocks are accessed after being deallocated, creating a use-after-free condition. This memory corruption occurs during the processing of multimedia content through the mediaserver daemon, which operates with elevated privileges due to its role in system-level media processing. When an attacker crafts a malicious application that triggers this specific sequence of operations, the vulnerability can be exploited to execute arbitrary code in the context of the mediaserver process, which typically runs with system-level privileges. The vulnerability specifically enables privilege escalation attacks that can result in gaining Signature or SignatureOrSystem access levels, representing a significant elevation from standard application permissions.
The operational impact of this vulnerability is severe as it provides attackers with the capability to achieve system-level compromise through a crafted application that leverages the memory corruption flaw. The mediaserver process operates with broad system privileges and is responsible for handling multimedia operations across the entire Android ecosystem, making it an attractive target for attackers seeking persistent system access. This vulnerability can be exploited remotely through malicious media files or applications that trigger the specific code path leading to the use-after-free condition, potentially allowing attackers to install malicious applications, access sensitive system data, or maintain persistent backdoor access to affected devices. The exploitation demonstrates characteristics consistent with the CWE-416 use-after-free vulnerability pattern, where memory is accessed after it has been freed, creating a potential for arbitrary code execution.
Mitigation strategies for this vulnerability require immediate application of the security patches released by Google as part of their regular security updates, specifically targeting the Android versions mentioned in the vulnerability description. System administrators and device manufacturers should prioritize deployment of the July 2016 security updates that address this specific memory management flaw in the video decoding component. The vulnerability also highlights the importance of input validation and proper memory management practices in system-level components, aligning with ATT&CK technique T1068 which covers exploit for privilege escalation. Organizations should implement robust application sandboxing measures and monitor for suspicious media processing activities, as this vulnerability can be exploited through legitimate media playback functionality, making detection challenging. The fix typically involves proper memory deallocation and access control mechanisms that prevent the reuse of freed memory blocks in the video decoding pipeline, effectively closing the privilege escalation vector that attackers can leverage to gain elevated system access through the mediaserver process.