CVE-2017-13837 in macOS
Summary
by MITRE
An issue was discovered in certain Apple products. macOS before 10.13 is affected. The issue involves the "Installer" component. It does not properly restrict an app's entitlements for accessing the FileVault unlock key.
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Analysis
by VulDB Data Team • 01/20/2020
The vulnerability identified as CVE-2017-13837 represents a critical entitlement restriction flaw within Apple's macOS installer component that affects versions prior to 10.13. This security weakness resides in the installer's handling of application entitlements, specifically concerning FileVault encryption key access permissions. The issue demonstrates a fundamental failure in macOS's entitlement validation mechanisms, where applications installed through the installer process can potentially acquire unauthorized access to critical system resources. This flaw operates at the intersection of macOS security architecture and application sandboxing principles, creating an avenue for privilege escalation attacks.
The technical implementation of this vulnerability stems from improper entitlement validation within the installer framework, allowing malicious or compromised applications to inherit or acquire FileVault unlock key access permissions that should be strictly restricted. This represents a direct violation of the principle of least privilege and demonstrates a failure in macOS's entitlement management system. The installer component fails to properly sanitize or validate the entitlements granted to applications during the installation process, enabling applications to potentially access encryption keys used for FileVault volume decryption. This flaw falls under the category of improper access control as defined by CWE-284 and represents a privilege escalation vulnerability that can be exploited by attackers to bypass full disk encryption protections.
The operational impact of this vulnerability extends beyond simple unauthorized access to FileVault keys, as it fundamentally undermines the security model of macOS full disk encryption. Attackers could potentially exploit this weakness to gain access to encrypted volumes without proper authentication, effectively neutralizing the protection provided by FileVault encryption. This vulnerability creates a persistent threat vector that remains active until the system is updated to a patched version, and it can be exploited by both local attackers with system access and potentially remote attackers in specific scenarios. The attack surface is particularly concerning because it affects the core installer functionality that is frequently used during system maintenance and software installation processes, making exploitation more likely and more persistent than in other security flaws.
Organizations and individual users should prioritize immediate remediation through macOS updates to version 10.13 or later, as this vulnerability represents a significant risk to data confidentiality and system integrity. The recommended mitigation strategy includes not only applying the official macOS security patches but also implementing additional monitoring for unauthorized entitlement changes and conducting security assessments of installed applications. This vulnerability aligns with ATT&CK technique T1068, which covers privilege escalation through local exploits, and demonstrates the importance of maintaining up-to-date system configurations to prevent exploitation of installer-based security flaws. Security teams should also consider implementing application whitelisting policies and monitoring for unusual entitlement modifications during installation processes to detect potential exploitation attempts. The vulnerability highlights the critical need for comprehensive entitlement management across all system components and serves as a reminder of the importance of proper access control validation in security-sensitive contexts.