CVE-2016-1773 in Mac OS X
Summary
by MITRE
The code-signing subsystem in Apple OS X before 10.11.4 does not properly verify file ownership, which allows local users to determine the existence of arbitrary files via unspecified vectors.
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Analysis
by VulDB Data Team • 11/12/2024
The vulnerability identified as CVE-2016-1773 resides within the code-signing subsystem of Apple's macOS operating system, specifically affecting versions prior to 10.11.4. This weakness represents a significant security flaw that undermines the integrity verification mechanisms designed to protect system files and applications from unauthorized modifications. The issue manifests in the subsystem's improper handling of file ownership verification during code-signing operations, creating an exploitable condition that can be leveraged by local adversaries.
The technical flaw stems from insufficient validation of file ownership attributes within the code-signing verification process. When macOS attempts to verify the authenticity and integrity of signed code, the subsystem fails to properly enforce ownership checks that should prevent unauthorized access to file system resources. This improper verification allows malicious users to craft specific requests that can probe the existence of files within the system without requiring elevated privileges. The unspecified vectors mentioned in the description suggest that the vulnerability can be exploited through multiple pathways within the code-signing framework, making it particularly challenging to defend against through traditional perimeter security measures.
From an operational perspective, this vulnerability enables local users to perform reconnaissance activities that would normally be restricted to privileged operations. Attackers can leverage this weakness to map out the file system structure, identify sensitive files, and potentially discover system configurations that could aid in further exploitation attempts. The ability to determine file existence without proper authorization creates a foundation for more sophisticated attacks, including privilege escalation and information disclosure operations. This type of vulnerability is particularly dangerous in environments where local access is not strictly controlled, as it can provide attackers with valuable intelligence for targeting other system components.
The impact of CVE-2016-1773 aligns with CWE-200, which addresses "Information Exposure," and demonstrates how improper access control mechanisms can lead to unauthorized information disclosure. From an adversary perspective, this vulnerability fits within the ATT&CK framework under the technique T1083, "File and Directory Discovery," as it enables attackers to enumerate system files and directories. The vulnerability also relates to T1552, "Unsecured Credentials," as it can be used to discover sensitive files that might contain authentication information or system keys. Security professionals should consider this weakness as part of a broader attack surface analysis, particularly in environments where code-signing is heavily relied upon for system integrity verification.
Mitigation strategies for this vulnerability primarily focus on updating to Apple macOS 10.11.4 or later versions where the code-signing subsystem properly enforces file ownership verification. System administrators should implement comprehensive patch management processes to ensure all macOS systems receive timely updates. Additional defensive measures include monitoring for unusual file system access patterns that might indicate exploitation attempts, implementing strict access controls for local user accounts, and conducting regular security assessments of code-signing configurations. Organizations should also consider deploying endpoint detection and response solutions that can identify anomalous behavior related to code-signing operations and file system enumeration activities. The vulnerability highlights the critical importance of proper access control enforcement in security subsystems and demonstrates how seemingly minor implementation flaws can have significant security implications.