CVE-2016-3299 in Windows
Summary
by MITRE
Microsoft Windows Vista SP2, Windows Server 2008 SP2 and R2 SP1, Windows 7 SP1, Windows 8.1, Windows Server 2012 Gold and R2, Windows RT 8.1, and Windows 10 Gold and 1511 allow remote attackers to hijack network traffic or bypass intended Enhanced Protected Mode (EPM) or application container protection mechanisms, and consequently render untrusted content in a browser, by leveraging how NetBIOS validates responses, aka "NetBIOS Spoofing Vulnerability."
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Analysis
by VulDB Data Team • 04/07/2017
The CVE-2016-3299 vulnerability represents a critical network protocol flaw affecting multiple Microsoft Windows operating systems including Vista SP2 through Windows 10 1511. This vulnerability stems from improper validation of NetBIOS responses within the Windows networking stack, creating a pathway for remote attackers to manipulate network traffic flows and bypass crucial security mechanisms. The flaw specifically targets the Enhanced Protected Mode (EPM) and application container protection systems that are designed to isolate untrusted content and prevent privilege escalation attacks. The vulnerability's impact extends beyond simple network interception as it fundamentally undermines the security boundaries that separate trusted and untrusted network contexts.
The technical implementation of this vulnerability exploits weaknesses in how NetBIOS name resolution operates within Windows environments. When systems receive NetBIOS responses, they fail to properly validate the authenticity of these responses, allowing malicious actors to inject false responses into network traffic. This spoofing capability enables attackers to redirect network requests to malicious endpoints while maintaining the appearance of legitimate network communication. The vulnerability operates at the transport layer of the network stack, leveraging the inherent trust relationships between network entities to establish unauthorized communication channels. This flaw aligns with CWE-20, which describes improper input validation, and specifically demonstrates how inadequate validation of network responses can lead to security bypass scenarios.
The operational impact of this vulnerability is severe as it allows attackers to perform man-in-the-middle attacks while simultaneously circumventing application sandboxing protections. When attackers successfully exploit this vulnerability, they can redirect users to malicious websites, inject content into legitimate browsing sessions, or redirect network traffic to attacker-controlled servers. The bypass of EPM protection mechanisms means that even when users are browsing with enhanced security settings, the vulnerability can be exploited to render untrusted content in browser contexts that should remain isolated. This represents a significant compromise of the security model that Windows implements to protect users from malicious web content, effectively nullifying the layered security approaches that Microsoft has implemented in their operating systems.
The attack vector for CVE-2016-3299 requires network access to the target system and can be executed remotely without requiring authentication or elevated privileges. Attackers typically leverage the vulnerability by positioning themselves on the same network segment as the target or by exploiting network infrastructure that allows them to intercept and inject NetBIOS responses. The vulnerability is particularly concerning because it affects a broad range of Windows operating systems, making it a high-value target for attackers seeking maximum impact. Organizations implementing network monitoring solutions should be aware that this vulnerability may manifest as unusual NetBIOS traffic patterns or unexpected network redirection behaviors. The ATT&CK framework categorizes this vulnerability under network infiltration techniques, specifically targeting the network traffic manipulation and privilege escalation capabilities that enable more sophisticated attacks.
Mitigation strategies for CVE-2016-3299 primarily focus on network-level protections and system updates. Microsoft released patches in their regular security updates that addressed the underlying NetBIOS validation issues, requiring system administrators to apply these updates promptly across all affected systems. Network segmentation and firewall rules can help limit the exposure of vulnerable systems to potential attackers, particularly by blocking NetBIOS traffic between trusted and untrusted network segments. Additionally, implementing network monitoring solutions that can detect anomalous NetBIOS response patterns can help identify exploitation attempts before they succeed. Organizations should also consider disabling NetBIOS name resolution where possible, as this reduces the attack surface for this particular vulnerability. The vulnerability demonstrates the importance of maintaining up-to-date security patches and the critical need for organizations to have robust vulnerability management processes in place to address such widespread security flaws that affect multiple operating system versions simultaneously.