CVE-2016-2476 in Android
Summary
by MITRE
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 2016-06-01 does not validate OMX buffer sizes, which allows attackers to gain privileges via a crafted application, as demonstrated by obtaining Signature or SignatureOrSystem access, aka internal bug 27207275.
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Analysis
by VulDB Data Team • 01/18/2019
The vulnerability identified as CVE-2016-2476 resides within the mediaserver component of various Android versions, specifically affecting 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 the 2016-06-01 security update. This issue represents a critical privilege escalation flaw that stems from inadequate input validation within the OpenMAX (OMX) buffer handling mechanisms. The mediaserver process operates with elevated privileges to manage multimedia operations across the Android system, making it a prime target for attackers seeking to elevate their access levels. The vulnerability manifests when the system fails to properly validate buffer sizes allocated for OMX operations, creating opportunities for memory corruption and unauthorized privilege escalation.
The technical flaw exploited in this vulnerability relates to improper buffer size validation within the OMX component of the Android media framework, which is categorized under CWE-129 - Improper Validation of Array Index. Attackers can craft malicious applications that manipulate OMX buffer parameters to trigger buffer overflow conditions or memory corruption within the mediaserver process. This allows adversaries to execute arbitrary code with system-level privileges, ultimately enabling them to obtain Signature or SignatureOrSystem level access. The exploitation process typically involves carefully constructed media files or streaming content that, when processed by the vulnerable mediaserver, causes memory corruption leading to privilege escalation. The vulnerability is particularly dangerous because it leverages the legitimate media processing capabilities of Android to achieve unauthorized system access, making detection challenging.
The operational impact of CVE-2016-2476 extends beyond simple privilege escalation to encompass potential full system compromise and data exfiltration capabilities. When successfully exploited, attackers can gain access to sensitive system resources, install malicious applications with system-level permissions, and potentially access encrypted data stored on the device. The vulnerability affects a wide range of Android devices that were in active use during the affected time periods, creating a substantial attack surface for threat actors. The privilege escalation to Signature or SignatureOrSystem access level allows attackers to bypass normal application sandboxing mechanisms and access protected system components, including the ability to sign applications with system signatures. This capability enables attackers to create malicious applications that can masquerade as legitimate system applications, further complicating detection and mitigation efforts.
Mitigation strategies for CVE-2016-2476 primarily focus on immediate system updates and patch management, as the vulnerability was addressed through Android security updates released in June 2016. Organizations and users should prioritize applying the relevant security patches to affected Android versions, particularly updating to Android 4.4.4, 5.0.2, 5.1.1, or the corresponding 2016-06-01 security update. Additionally, implementing network-based security controls such as mobile device management solutions can help restrict potentially malicious applications from being installed on affected devices. Security monitoring should include detection of anomalous media processing activities that might indicate exploitation attempts, and endpoint protection solutions should be configured to monitor for suspicious privilege escalation behaviors. The vulnerability also aligns with ATT&CK technique T1068 - Exploitation for Privilege Escalation, where attackers leverage system vulnerabilities to gain elevated access rights, and T1059 - Command and Scripting Interpreter, as exploitation often involves crafting and executing malicious media content to trigger the vulnerability. Device manufacturers and security teams should also consider implementing runtime protections and memory corruption detection mechanisms to help prevent exploitation of similar buffer validation flaws in the future.