CVE-2016-4713 in macOS
Summary
by MITRE
CoreDisplay in Apple OS X before 10.12 allows attackers to view arbitrary users screens by leveraging screen-sharing access.
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Analysis
by VulDB Data Team • 09/20/2022
The vulnerability identified as CVE-2016-4713 resides within CoreDisplay, a fundamental component of Apple's macOS operating system that manages display services and graphics rendering. This flaw exists in versions prior to macOS 10.12, creating a significant security gap that allows unauthorized individuals to gain access to screen content from other user sessions on the same system. The vulnerability specifically exploits the screen-sharing functionality that is designed for legitimate collaborative purposes but can be abused to monitor or capture display information from adjacent user sessions.
The technical implementation of this vulnerability stems from inadequate access controls within the CoreDisplay framework. When screen-sharing features are enabled, the system should properly isolate display sessions to prevent cross-user information leakage. However, the flaw allows an attacker with screen-sharing access to potentially view or capture screen content from other user sessions, effectively bypassing the normal security boundaries that should exist between different user contexts. This represents a privilege escalation issue where a user with limited screen-sharing permissions can gain unauthorized access to display information from other users.
The operational impact of this vulnerability extends beyond simple information disclosure, as it creates a persistent surveillance capability that can be exploited for various malicious purposes. An attacker could use this vulnerability to monitor sensitive user activities, capture login credentials, access confidential documents, or observe personal communications across different user sessions. The vulnerability is particularly concerning because it operates at the system level where display services are managed, making it difficult to detect through normal security monitoring procedures. This type of flaw aligns with CWE-284 Access Control Issues, specifically addressing insufficient access control mechanisms that allow unauthorized information access.
The attack vector for this vulnerability typically involves an attacker who already possesses screen-sharing privileges or can somehow acquire them through other means. Once these privileges are obtained, the attacker can leverage the CoreDisplay flaw to access screen content from other user sessions without proper authentication. This vulnerability demonstrates the importance of proper privilege separation in system components and highlights how display management services can become attack surfaces when access controls are insufficient. The flaw represents a failure in the principle of least privilege, where system components should not be able to access information beyond their intended scope.
Mitigation strategies for CVE-2016-4713 primarily involve updating to macOS 10.12 or later versions where Apple has addressed the underlying access control issues in CoreDisplay. Organizations should implement comprehensive patch management procedures to ensure all systems are updated promptly. Additionally, administrators should review and restrict screen-sharing permissions to only those users who require such access for legitimate business purposes. Network monitoring solutions should be configured to detect unusual screen-sharing activity patterns that might indicate exploitation attempts. This vulnerability exemplifies the ATT&CK technique T1056.001 Credential Access: Brute Force, as it enables unauthorized access to user sessions through legitimate system features. System hardening practices should include disabling screen-sharing functionality when not required and implementing proper user access controls to minimize the attack surface. The remediation process should also involve security audits to identify and revoke unnecessary screen-sharing permissions that could be exploited to leverage this vulnerability.