CVE-2016-1774 in OS X Server
Summary
by MITRE
The Time Machine server in Server App in Apple OS X Server before 5.1 does not notify the user about ignored permissions during a backup, which makes it easier for remote attackers to obtain sensitive information in opportunistic circumstances by reading backup data that lacks intended restrictions.
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Analysis
by VulDB Data Team • 07/10/2022
The vulnerability described in CVE-2016-1774 resides within Apple's OS X Server Time Machine implementation, specifically affecting versions prior to 5.1. This flaw represents a significant security oversight in the backup system's permission handling mechanisms, creating a scenario where sensitive data can be accessed through unintended pathways. The issue manifests when the Time Machine server fails to properly communicate to users when backup operations encounter permission restrictions that result in data being excluded from backups. This technical deficiency creates a false sense of security for administrators who may believe their backup configurations are properly protecting sensitive information, while in reality, data that should be restricted remains accessible through the backup system.
The core technical flaw involves the absence of proper error notification mechanisms within the Time Machine server's backup process. When the system encounters files or directories with restrictive permissions that prevent backup inclusion, it silently ignores these restrictions rather than alerting administrators to the potential exposure. This behavior creates a condition where attackers can exploit the system by strategically placing sensitive data in locations that would normally be protected but are instead silently excluded from backups due to permission issues. The vulnerability operates under CWE-200, which addresses information exposure through improper error handling, and represents a classic case of insufficient logging and monitoring that allows security controls to be bypassed without detection.
From an operational impact perspective, this vulnerability significantly weakens the security posture of organizations relying on Apple's Time Machine server for backup operations. Attackers can leverage this flaw to access sensitive information that was presumably protected by file permissions, potentially including confidential documents, system configuration files, user data, and other restricted resources. The opportunistic nature of this attack means that even if administrators implement proper permission controls, the backup system's failure to notify about ignored permissions creates an exploitable gap. This vulnerability directly aligns with ATT&CK technique T1005, which covers data from local system, and T1070, covering indicator removal on host, as it allows for data exfiltration without proper audit trails or system notifications.
The mitigation strategy for this vulnerability requires immediate upgrade to Apple OS X Server version 5.1 or later, which addresses the permission notification flaw in the Time Machine server implementation. Organizations should also conduct comprehensive audits of their backup configurations to identify any files or directories that may have been silently excluded from backups due to permission restrictions. System administrators should implement additional monitoring mechanisms to detect unusual backup patterns or access attempts to backup repositories, ensuring that any unauthorized data access attempts are properly logged and investigated. The vulnerability demonstrates the critical importance of proper error handling and user notification in security-critical systems, as the lack of visibility into permission-related issues created an exploitable condition that could be leveraged by threat actors to gain access to sensitive information that should have been protected by standard file permission controls.