CVE-2018-4211 in iOS
Summary
by MITRE
An issue was discovered in certain Apple products. iOS before 11.4 is affected. macOS before 10.13.5 is affected. tvOS before 11.4 is affected. watchOS before 4.3.1 is affected. The issue involves the "FontParser" component. It allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption and application crash) via a crafted font file.
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Analysis
by VulDB Data Team • 03/20/2023
The vulnerability identified as CVE-2018-4211 represents a critical security flaw within Apple's font parsing infrastructure affecting multiple operating systems including iOS, macOS, tvOS, and watchOS. This vulnerability resides within the FontParser component which is responsible for processing font files within the Apple ecosystem. The flaw manifests when the system encounters specially crafted font files that trigger memory corruption during the parsing process. According to the Common Weakness Enumeration framework, this vulnerability maps to CWE-125: Out-of-bounds Read, as the parser fails to properly validate font data boundaries leading to memory access violations. The issue demonstrates characteristics consistent with heap-based buffer overflow conditions where attacker-controlled data can overwrite adjacent memory regions.
The operational impact of this vulnerability extends beyond simple denial of service scenarios to encompass full arbitrary code execution capabilities. Remote attackers can exploit this weakness by delivering maliciously crafted font files through various attack vectors including email attachments, web downloads, or malicious websites. When a vulnerable system processes these crafted fonts, the corrupted memory state can be leveraged to execute attacker-controlled code with the privileges of the affected application. This represents a significant escalation from typical denial of service conditions to full system compromise. The vulnerability affects all versions prior to the respective patched releases, with iOS 11.4, macOS 10.13.5, tvOS 11.4, and watchOS 4.3.1 serving as the first versions to include fixes for this issue.
The attack surface for CVE-2018-4211 is particularly concerning given the ubiquity of font processing across Apple's platforms. Font files are commonly encountered during normal system operation through various applications including web browsers, email clients, and document viewers. The vulnerability's remote exploitability means that attackers do not require physical access to target devices or user interaction beyond normal system usage patterns. From an adversarial perspective, this vulnerability aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter: PowerShell and similar execution methods, though the actual exploitation occurs at the memory corruption level. The memory corruption nature suggests that attackers could potentially leverage this for privilege escalation or data exfiltration attacks. Security researchers have noted that the vulnerability's exploitation complexity is relatively low, making it attractive for automated attack toolkits and widespread exploitation campaigns.
Mitigation strategies for CVE-2018-4211 primarily focus on immediate system updates to the patched versions of affected operating systems. Organizations should prioritize deployment of iOS 11.4, macOS 10.13.5, tvOS 11.4, and watchOS 4.3.1 across all affected devices. Additional defensive measures include implementing network-based controls to restrict font file downloads and implementing application whitelisting policies to limit font processing to trusted sources. System administrators should consider monitoring for unusual font processing activities and implement sandboxing techniques where possible. The vulnerability highlights the importance of input validation and bounds checking in font parsing libraries, reinforcing industry best practices outlined in secure coding guidelines. Organizations should also conduct vulnerability assessments to identify any custom applications or services that may be processing font files and ensure they implement proper input sanitization measures. Regular security updates and patch management programs become critical in defending against similar vulnerabilities in font processing components.