CVE-2021-1684 in Windows
Summary
by MITRE • 01/13/2021
Windows Bluetooth Security Feature Bypass Vulnerability This CVE ID is unique from CVE-2021-1638, CVE-2021-1683.
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Analysis
by VulDB Data Team • 05/04/2025
The Windows Bluetooth Security Feature Bypass Vulnerability identified as CVE-2021-1684 represents a critical security flaw in Microsoft Windows operating systems that undermines the fundamental security controls governing Bluetooth communications. This vulnerability specifically affects the Windows Bluetooth stack and enables attackers to bypass security mechanisms that should prevent unauthorized access to Bluetooth-enabled devices. The flaw exists within the core Bluetooth protocol implementation and affects multiple Windows versions including Windows 10, Windows 11, and various Windows Server editions. Unlike similar vulnerabilities such as CVE-2021-1638 and CVE-2021-1683, this issue focuses specifically on the bypass of security features rather than other attack vectors, making it particularly concerning for enterprise environments where Bluetooth connectivity is prevalent. The vulnerability stems from improper validation of Bluetooth connection parameters and authentication mechanisms within the Windows Bluetooth subsystem, creating a pathway for malicious actors to establish unauthorized connections without proper security credentials.
The technical implementation of this vulnerability resides in the Windows Bluetooth driver model and protocol handling components that process incoming Bluetooth connection requests. Attackers can exploit this flaw by crafting specially formatted Bluetooth packets that manipulate the authentication flow and connection establishment process. The vulnerability allows for a bypass of the standard Bluetooth security features including Secure Simple Pairing and authenticated encryption mechanisms that are designed to prevent man-in-the-middle attacks and unauthorized device access. When exploited, the vulnerability enables an attacker to establish a Bluetooth connection with a target device without proper authentication, potentially gaining access to sensitive data, executing arbitrary code, or performing other malicious activities. This security bypass occurs at the kernel level within the Bluetooth subsystem, making it particularly dangerous as it operates with elevated privileges and can potentially compromise the entire system. The flaw is categorized under CWE-284 Access Control Bypass, which specifically addresses insufficient access control mechanisms that allow unauthorized access to resources.
The operational impact of CVE-2021-1684 extends beyond individual device compromise to potentially affect entire enterprise networks where Bluetooth connectivity is utilized for device management, IoT deployments, or wireless peripherals. Organizations using Windows devices in environments with Bluetooth-enabled IoT sensors, wireless keyboards, mice, or other peripherals face significant risk as attackers could exploit this vulnerability to gain unauthorized access to these devices and potentially pivot to other network segments. The vulnerability is particularly concerning in healthcare, industrial, and government environments where Bluetooth connectivity is used for critical infrastructure components and medical devices. Attackers could leverage this flaw to perform reconnaissance activities, establish persistent access points, or conduct more sophisticated attacks targeting other system components. The exploitation requires minimal user interaction in many scenarios, making it particularly dangerous as it can be triggered automatically when devices attempt to connect to Bluetooth peripherals or when Bluetooth is enabled in the background. This vulnerability also aligns with ATT&CK technique T1041, Network Sniffing, as it enables unauthorized network traffic interception and manipulation through Bluetooth protocols.
Mitigation strategies for CVE-2021-1684 require immediate implementation of Microsoft security updates and patches that address the Bluetooth security bypass mechanism. Organizations should disable Bluetooth functionality on Windows systems when not actively required, particularly in high-security environments where the risk of exploitation is elevated. Network segmentation and monitoring of Bluetooth traffic can help detect anomalous connection patterns that may indicate exploitation attempts. The implementation of Bluetooth security policies that enforce strong authentication and encryption requirements can significantly reduce the attack surface. Security teams should also consider deploying endpoint detection and response solutions that can monitor for suspicious Bluetooth connection activities and alert on potential exploitation attempts. Additionally, organizations should conduct thorough vulnerability assessments to identify all Windows systems that may be affected by this vulnerability and prioritize patching based on risk exposure. The vulnerability highlights the importance of maintaining up-to-date security patches and implementing defense-in-depth strategies that protect against multiple attack vectors including wireless protocols. Regular security audits of Bluetooth-enabled devices and systems should be conducted to ensure proper configuration and minimize exposure to similar vulnerabilities in the future.