CVE-2018-4251 in macOS
Summary
by MITRE
An issue was discovered in certain Apple products. macOS before 10.13.5 is affected. The issue involves the "Firmware" component. It allows attackers to modify the EFI flash-memory region that a crafted app that has root access.
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Analysis
by VulDB Data Team • 03/19/2023
The vulnerability identified as CVE-2018-4251 represents a critical security flaw in Apple's macOS operating system affecting versions prior to 10.13.5. This issue resides within the firmware component of the system, specifically targeting the EFI (Extensible Firmware Interface) flash-memory region which serves as a crucial bridge between hardware and operating system initialization processes. The flaw stems from insufficient access controls and validation mechanisms within the firmware update and modification pathways, creating an exploitable condition that allows malicious actors to gain unauthorized access to low-level system components.
The technical exploitation of this vulnerability occurs when a malicious application with root privileges attempts to modify the EFI flash-memory region through improper validation checks. This weakness enables attackers to execute code at a level below the operating system, effectively bypassing traditional security controls and operating system protections. The vulnerability specifically relates to improper privilege escalation mechanisms within the firmware update framework, allowing an attacker with root access to manipulate critical system firmware components that should remain protected from modification. This represents a fundamental breakdown in the security model of the system, as the EFI region typically requires specialized authentication and authorization mechanisms that are bypassed in this scenario.
The operational impact of CVE-2018-4251 extends far beyond typical application-level vulnerabilities, as it compromises the foundational security of the entire system architecture. Attackers who successfully exploit this vulnerability can potentially install persistent backdoors, modify boot processes, or establish rootkits that operate below the operating system level, making detection extremely difficult. The implications are particularly severe in enterprise environments where macOS systems may be targeted for advanced persistent threats, as the attacker gains access to a level of system control that can persist across reboots and operating system reinstalls. This vulnerability aligns with CWE-284, which describes improper access control in software systems, and represents a significant weakening of the principle of least privilege in firmware management.
Mitigation strategies for this vulnerability primarily focus on immediate system updates to macOS 10.13.5 or later versions where Apple has implemented proper access controls and validation mechanisms for EFI flash-memory modifications. Organizations should also implement comprehensive monitoring of system boot processes and firmware integrity checks as part of their security operations. The remediation process requires careful consideration of the potential impact on system stability, as firmware modifications can affect hardware compatibility and system functionality. Security teams should also review and strengthen access control policies to minimize the risk of unauthorized root access, as the vulnerability specifically requires an attacker to already possess root privileges to exploit the firmware modification pathway. This vulnerability demonstrates the critical importance of maintaining up-to-date firmware and operating system components as outlined in industry best practices for endpoint security management.