CVE-2016-3895 in Android
Summary
by MITRE
Integer overflow in the Region::unflatten function in libs/ui/Region.cpp in mediaserver in Android 6.x before 2016-09-01 and 7.0 before 2016-09-01 allows attackers to obtain sensitive information via a crafted application, aka internal bug 29983260.
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Analysis
by VulDB Data Team • 09/15/2022
The vulnerability identified as CVE-2016-3895 represents a critical integer overflow flaw within the Android mediaserver component that affects versions 6.x and 7.0 prior to the specified security patch date. This issue resides in the Region::unflatten function located in the libs/ui/Region.cpp file, which is part of the Android framework's user interface subsystem. The mediaserver process serves as a critical system component responsible for handling multimedia operations and maintaining secure communication between various Android services and applications, making it a prime target for privilege escalation and information disclosure attacks.
The technical nature of this vulnerability stems from improper input validation within the Region::unflatten function where integer overflow occurs during the processing of serialized region data structures. When a malicious application crafts specially designed input parameters, the function fails to properly validate the size calculations, leading to arithmetic overflow conditions that can result in memory corruption. This flaw specifically manifests when the system attempts to reconstruct region objects from flattened data representations, where the overflow allows attackers to manipulate memory layout and potentially access sensitive data structures that should remain protected. The vulnerability operates at the kernel level within the Android framework, leveraging the inherent trust relationships between system components to bypass normal security boundaries.
The operational impact of CVE-2016-3895 extends beyond simple information disclosure, as it creates opportunities for more sophisticated attacks within the Android security model. An attacker who successfully exploits this vulnerability can potentially extract sensitive information from memory regions that contain credentials, encryption keys, or other confidential data structures. The flaw is particularly dangerous because it operates within the mediaserver process which typically runs with elevated privileges and has access to various system resources. This vulnerability aligns with CWE-190, which specifically addresses integer overflow conditions, and represents a classic example of how improper integer handling can lead to security breaches. The attack vector requires only a crafted application, making it particularly concerning as it can be executed without physical access to the device or specialized hardware.
Security mitigations for this vulnerability primarily involve applying the official Android security patches released in September 2016, which address the integer overflow condition in the Region::unflatten function through proper input validation and size checking mechanisms. System administrators and device manufacturers should prioritize immediate deployment of these updates across all affected Android versions. Additionally, implementing proper code review processes that focus on integer arithmetic handling and memory management can help prevent similar issues in future development cycles. The vulnerability demonstrates the importance of input validation in system-level code and highlights the need for comprehensive security testing of framework components that handle serialized data. Organizations should also consider implementing runtime monitoring and anomaly detection systems to identify potential exploitation attempts. From an ATT&CK perspective, this vulnerability maps to techniques involving privilege escalation and information gathering, specifically targeting the system services layer and leveraging the trust relationships between system components to achieve unauthorized access to sensitive information.