CVE-2018-4229 in macOS
Summary
by MITRE
An issue was discovered in certain Apple products. macOS before 10.13.5 is affected. The issue involves the "Grand Central Dispatch" component. It allows attackers to bypass a sandbox protection mechanism by leveraging the misparsing of entitlement plists.
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Analysis
by VulDB Data Team • 03/19/2023
The vulnerability identified as CVE-2018-4229 represents a critical sandbox bypass issue within Apple's Grand Central Dispatch (GCD) framework affecting macOS versions prior to 10.13.5. This flaw resides in the entitlement plist parsing mechanism that governs application permissions and access controls within the operating system's security architecture. The vulnerability stems from improper handling of entitlement data structures that are crucial for defining which privileges applications can access within the sandboxed environment. When an application attempts to parse entitlement plists, the GCD component fails to properly validate or sanitize the input data, creating a potential pathway for malicious actors to manipulate the entitlement parsing process.
The technical exploitation of this vulnerability leverages the misparsing behavior of entitlement plists to elevate privileges beyond the intended sandbox boundaries. Attackers can craft specially formatted entitlement plists that, when processed by the affected GCD component, result in incorrect permission assignments or bypass of security checks. This misinterpretation occurs during the dynamic loading and evaluation of entitlement data, where the system fails to properly validate the structure and content of the plist files. The flaw essentially allows unauthorized code execution with elevated privileges that would normally be restricted by the sandbox mechanism, effectively undermining the fundamental security model that separates applications from system resources and other processes.
From an operational impact perspective, this vulnerability presents a significant risk to macOS environments as it enables attackers to circumvent the sandbox protection that is central to Apple's security architecture. The ability to bypass sandbox restrictions means that malicious applications could potentially access sensitive system resources, read protected files, modify system configurations, or execute arbitrary code with elevated privileges. This vulnerability is particularly concerning because it affects the core dispatch mechanism that underpins many system operations and application behaviors, potentially allowing for widespread privilege escalation attacks. The impact extends beyond individual applications to affect the entire operating system security model, as the sandbox bypass could enable attackers to move laterally within the system or access data that should remain isolated.
Security researchers have categorized this vulnerability under CWE-225, which addresses improper handling of potentially dangerous data, and it aligns with ATT&CK technique T1055.011 for privilege escalation through sandbox bypass mechanisms. The vulnerability demonstrates how seemingly minor parsing flaws in core system components can create substantial security implications, particularly when they affect fundamental security controls like sandboxing. Organizations should prioritize patching affected systems immediately, as the vulnerability provides attackers with a direct pathway to bypass critical security controls. The remediation involves updating to macOS 10.13.5 or later versions where Apple has implemented proper entitlement plist validation and parsing mechanisms. System administrators should also conduct thorough security assessments to identify any applications that might be exploiting this vulnerability or that could be vulnerable due to custom entitlement configurations. Additionally, monitoring for unusual entitlement parsing activities or privilege escalation attempts should be implemented as part of defensive measures against this specific vulnerability class.