CVE-2021-30731 in macOS
Summary
by MITRE • 09/08/2021
This issue was addressed with improved checks. This issue is fixed in macOS Big Sur 11.4, Security Update 2021-004 Catalina. An unprivileged application may be able to capture USB devices.
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Analysis
by VulDB Data Team • 09/11/2021
This vulnerability represents a significant security flaw in apple's macOS operating system that allowed unprivileged applications to potentially capture and access USB devices without proper authorization. The issue stems from insufficient access controls and validation mechanisms within the system's USB device handling architecture, creating an avenue for malicious software to exploit system resources. The vulnerability specifically affects systems running macOS Big Sur 11.4 and earlier versions, as well as certain Security Update 2021-004 Catalina releases, indicating a widespread impact across multiple operating system versions. This type of flaw falls under the category of privilege escalation and device access control failures that can lead to unauthorized system compromise.
The technical implementation of this vulnerability involves the improper validation of USB device access requests within the kernel-level drivers and system frameworks that manage hardware interactions. When applications attempt to communicate with USB devices, the system should enforce strict access controls to ensure only authorized processes can interact with specific hardware. However, the flaw allowed unprivileged applications to bypass these security checks and gain unauthorized access to USB device interfaces. This represents a critical failure in the principle of least privilege enforcement, where applications should only have access to system resources necessary for their legitimate operation. The vulnerability can be classified under CWE-284 (Improper Access Control) and potentially CWE-276 (Incorrect Permission Assignment) as it involves unauthorized access to system resources through flawed permission handling.
The operational impact of this vulnerability extends beyond simple unauthorized device access, potentially enabling sophisticated attack vectors that could compromise system integrity and user privacy. An attacker could leverage this flaw to capture sensitive data from USB devices such as keyboards, mice, or storage devices, potentially intercepting keystrokes, accessing encrypted data, or performing malicious operations on connected hardware. This capability could facilitate advanced persistent threats where adversaries maintain long-term access to systems through USB-based attack vectors. The vulnerability also aligns with several tactics described in the attack mitigation framework, particularly those involving privilege escalation and persistence mechanisms that leverage hardware access to maintain control over compromised systems.
Organizations and users should immediately apply the security updates provided by apple, specifically macOS Big Sur 11.4 and Security Update 2021-004 Catalina, to remediate this vulnerability. System administrators should conduct comprehensive vulnerability assessments to identify any potentially compromised systems and implement additional monitoring for unauthorized USB device access. The fix addresses the core access control issues by strengthening the validation mechanisms that govern USB device interactions, ensuring that only properly authorized applications can establish connections with hardware interfaces. Regular security audits should include verification of system update status and monitoring of USB device access logs to detect potential exploitation attempts. This vulnerability serves as a reminder of the critical importance of maintaining up-to-date security patches and implementing comprehensive device access controls to prevent unauthorized hardware interactions that could compromise overall system security posture.