CVE-2019-8568 in watchOS
Summary
by MITRE
A validation issue existed in the handling of symlinks. This issue was addressed with improved validation of symlinks. This issue is fixed in iOS 12.3, macOS Mojave 10.14.5, tvOS 12.3, watchOS 5.2.1. A local user may be able to modify protected parts of the file system.
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Analysis
by VulDB Data Team • 06/07/2024
The vulnerability identified as CVE-2019-8568 represents a critical file system validation flaw that emerged in Apple's operating systems, specifically affecting iOS 12.2 and earlier versions, macOS Mojave 10.14.4 and earlier, tvOS 12.2 and earlier, and watchOS 5.2 and earlier. This issue stems from inadequate symlink validation mechanisms that allowed malicious local users to exploit the system's file handling capabilities. The flaw demonstrates a fundamental weakness in the operating system's permission model and file system integrity controls, creating potential pathways for unauthorized modifications to protected system areas.
The technical implementation of this vulnerability involves the improper validation of symbolic links within the file system hierarchy, where the system fails to adequately verify the legitimacy and safety of symlink targets before processing them. This validation gap enables attackers to create or manipulate symbolic links that point to protected system directories or files, effectively bypassing normal access controls. The issue is classified under CWE-59 as a "Improper Link Resolution Without Limitations" which specifically addresses weaknesses in handling symbolic links and hard links. The vulnerability operates at the kernel level where file system operations are processed, making it particularly dangerous as it can potentially escalate privileges and allow access to system-critical components.
The operational impact of CVE-2019-8568 extends beyond simple file system manipulation, as it provides a local user with the capability to modify protected parts of the file system that should normally be restricted to system processes or administrators. This weakness creates a potential attack vector that could be exploited to modify system binaries, configuration files, or other protected resources that maintain system integrity and security policies. Attackers could leverage this vulnerability to install malicious code, modify system settings, or disable security features, fundamentally compromising the trust model of the operating system. The vulnerability's exploitation aligns with ATT&CK technique T1059.001 for Command and Scripting Interpreter and T1068 for Exploitation for Privilege Escalation, demonstrating how symlink manipulation can serve as a foundation for broader system compromise.
Apple's remediation for this vulnerability involved implementing enhanced symlink validation mechanisms across all affected platforms through updates to iOS 12.3, macOS Mojave 10.14.5, tvOS 12.3, and watchOS 5.2.1. These updates strengthened the file system's validation routines to properly check symlink targets against established security policies and access control lists. The fix addresses the core issue by ensuring that all symbolic link operations undergo rigorous validation before being processed, preventing maliciously crafted symlinks from gaining unauthorized access to protected system areas. System administrators should prioritize deployment of these security updates across all affected devices to prevent potential exploitation, as the vulnerability represents a significant risk to system integrity and user data protection. Organizations should also implement monitoring for suspicious file system activities and consider additional security measures such as sandboxing and file integrity monitoring to detect potential exploitation attempts.