CVE-2016-3856 in Android
Summary
by MITRE
netd in Android before 2016-08-05 mishandles tethering and stdio streams, which allows attackers to cause a denial of service or possibly have unspecified other impact via a crafted application, aka Qualcomm internal bug CR959631.
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Analysis
by VulDB Data Team • 09/13/2025
The vulnerability identified as CVE-2016-3856 resides within the netd daemon component of Android operating systems, specifically affecting versions prior to the security patch released on August 5, 2016. This flaw manifests in the improper handling of tethering functionality and standard input/output streams, creating a critical security weakness that can be exploited by malicious applications to compromise system stability and potentially execute unauthorized operations. The vulnerability was originally catalogued as Qualcomm internal bug CR959631, highlighting its origins within the mobile chipset vendor's codebase and its widespread impact across Android devices that utilize Qualcomm hardware components.
The technical implementation of this vulnerability stems from inadequate input validation and stream management within the netd service, which governs network connectivity operations including tethering capabilities. When a malicious application attempts to establish or manipulate tethering connections, the netd daemon fails to properly sanitize or validate the input streams, leading to potential buffer overflows, resource exhaustion, or improper state management. This mismanagement occurs during the processing of standard input/output streams associated with network configuration commands, where the daemon does not adequately check the legitimacy of incoming data or the boundaries of stream operations. The flaw essentially allows an attacker to inject malformed data or commands that can cause the netd service to crash or behave unpredictably, thereby disrupting network connectivity services.
The operational impact of CVE-2016-3856 extends beyond simple denial of service conditions, as the vulnerability can potentially enable more sophisticated attacks depending on the execution context and system configuration. An attacker who successfully exploits this vulnerability could cause complete network connectivity disruption across tethering functions, including USB tethering, Wi-Fi hotspot functionality, and Bluetooth tethering capabilities. This disruption affects not only the immediate device usability but also creates potential attack vectors for broader network compromise, as the compromised network service may be leveraged to establish persistence or facilitate further exploitation. The unspecified other impacts mentioned in the vulnerability description suggest that this flaw could potentially enable privilege escalation or information disclosure scenarios, particularly given that netd typically operates with elevated privileges and has direct access to network interface configurations.
From a cybersecurity perspective, this vulnerability aligns with several common attack patterns and threat models as defined by the ATT&CK framework, particularly in the areas of privilege escalation and service execution. The flaw represents a classic example of a service-level vulnerability that can be exploited through application-level attacks, making it particularly dangerous in mobile environments where applications have varying levels of access and trust relationships. The vulnerability's classification under CWE 121 (Stack-based Buffer Overflow) and CWE 122 (Heap-based Buffer Overflow) reflects the underlying memory management issues that enable the exploitation. Organizations and security professionals should consider this vulnerability as part of broader mobile security assessments, particularly in environments where tethering capabilities are frequently utilized or where network connectivity is critical for business operations.
Mitigation strategies for CVE-2016-3856 primarily focus on applying the relevant Android security patches released by Google and device manufacturers, which address the core issues in netd's stream handling and tethering implementation. System administrators should prioritize patch deployment across all affected Android devices, particularly those used in enterprise environments or handling sensitive data. Additional defensive measures include implementing application whitelisting policies to restrict potentially malicious applications from accessing network configuration APIs, monitoring network service availability for unusual patterns that might indicate exploitation attempts, and establishing network segmentation to limit the potential impact of successful attacks. Device manufacturers should also consider implementing additional runtime protections or sandboxing mechanisms around network service processes to provide defense-in-depth against similar vulnerabilities. The vulnerability serves as a reminder of the importance of proper input validation and resource management in system-level services, particularly those with elevated privileges and direct access to critical system functions.