CVE-2016-3878 in Android
Summary
by MITRE
decoder/ih264d_api.c in mediaserver in Android 6.x before 2016-09-01 mishandles the case of decoding zero MBs, which allows remote attackers to cause a denial of service (device hang or reboot) via a crafted media file, aka internal bug 29493002.
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Analysis
by VulDB Data Team • 09/15/2022
The vulnerability described in CVE-2016-3878 resides within the hardware-accelerated video decoding component of Android 6.0 Marshmallow, specifically in the ih264d_api.c file that manages the decoding process for H.264 video streams. This flaw represents a critical denial of service vulnerability that affects the mediaserver process responsible for handling multimedia content on Android devices. The issue manifests when the video decoder encounters a crafted media file containing zero macroblocks, a condition that the software fails to properly handle during the decoding sequence.
The technical root cause of this vulnerability stems from inadequate input validation within the video decoding pipeline where the system does not properly account for edge cases involving empty or minimal video data structures. When processing a specially crafted media file that contains zero macroblocks, the decoder enters an undefined state that leads to system instability. This condition triggers a device hang or forced reboot, effectively rendering the affected Android device unusable until manual intervention occurs. The vulnerability specifically impacts the H.264 decoder implementation in the hardware acceleration framework, which is designed to offload video processing from the main CPU to dedicated hardware components for improved performance.
From an operational perspective, this vulnerability presents a significant risk to Android users as it can be exploited remotely through malicious media files delivered via email attachments, messaging applications, web downloads, or malicious websites. The attack requires no user interaction beyond opening the crafted media file, making it particularly dangerous as it can be weaponized in phishing campaigns or social engineering attacks. The impact extends beyond simple inconvenience to potentially disrupting critical device functionality, especially in enterprise environments where mobile devices serve as primary communication tools. The vulnerability affects all Android 6.0 devices released prior to the security patch in September 2016, representing a substantial portion of the Android user base at that time.
Security researchers have classified this vulnerability under CWE-362, which deals with concurrent execution using shared resource with improper synchronization, as the decoder's handling of zero macroblock conditions creates race conditions and resource contention issues. The vulnerability also maps to ATT&CK technique T1203, which covers "Exploitation for Client Execution" where adversaries leverage system vulnerabilities to execute malicious code or cause system instability. Organizations should implement immediate mitigation strategies including applying the September 2016 security patches provided by Google, implementing network-based filtering to block suspicious media file types, and educating users about the risks of opening unknown media attachments. Additionally, mobile device management solutions should enforce automatic security updates and consider temporary restrictions on media file processing capabilities until full patches are deployed across all affected devices.