CVE-2016-4718 in tvOS
Summary
by MITRE
Buffer overflow in FontParser in Apple iOS before 10, OS X before 10.12, tvOS before 10, and watchOS before 3 allows remote attackers to obtain sensitive information from process memory via a crafted font file.
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Analysis
by VulDB Data Team • 09/21/2022
The vulnerability identified as CVE-2016-4718 represents a critical buffer overflow flaw within Apple's FontParser component that affected multiple operating systems including iOS versions prior to 10, macOS versions before 10.12, tvOS versions before 10, and watchOS versions before 3. This issue resides in the font parsing functionality that processes font files, specifically targeting the memory management mechanisms used when handling crafted font data. The vulnerability operates at the intersection of software security and multimedia processing, where improper bounds checking allows attackers to manipulate memory access patterns that ultimately expose sensitive information from process memory. The flaw stems from insufficient validation of font file structures, particularly when processing malformed or maliciously constructed font data that exceeds allocated buffer boundaries.
The technical exploitation of this vulnerability occurs when a malicious font file is processed by the affected systems, triggering a buffer overflow condition that can be leveraged to read arbitrary memory locations. This allows remote attackers to extract sensitive information such as cryptographic keys, user credentials, or application data that resides in the memory space of the affected processes. The vulnerability operates under the Common Weakness Enumeration framework as CWE-121, which describes heap-based buffer overflow conditions where insufficient bounds checking permits memory access beyond allocated buffers. The attack vector is classified as remote since the malicious font file can be delivered over network channels, making the vulnerability particularly dangerous for web-based attacks or email attachments. The specific nature of the flaw enables information disclosure rather than arbitrary code execution, though the information exposure can still result in significant security compromise.
From an operational perspective, this vulnerability impacts a broad range of Apple devices and operating systems, creating a substantial attack surface across mobile, desktop, and television platforms. The vulnerability's remote nature means that attackers can exploit it without physical access to devices, making it particularly concerning for enterprise environments where users may encounter malicious font files through various channels including email, web browsing, or file downloads. The affected systems are particularly vulnerable when processing font files in applications such as web browsers, email clients, or document viewers that utilize Apple's native font rendering capabilities. The information disclosure aspect means that attackers could potentially extract sensitive data that could be used for further attacks, including credential harvesting, privilege escalation, or targeted exploitation of other system components. This vulnerability also aligns with ATT&CK framework technique T1059, which covers execution through scripting or command-line interfaces, as the information exposure could enable attackers to craft more sophisticated attacks against affected systems.
The mitigation strategies for this vulnerability primarily involve applying the security patches released by Apple in their respective operating system updates. Organizations should prioritize updating affected systems to versions that contain the fixed FontParser implementation with proper bounds checking and memory management. Additionally, implementing network-based controls such as font file filtering or sandboxing mechanisms can provide additional protection layers. System administrators should also consider monitoring for unusual font processing activities or memory access patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of proper input validation in multimedia processing components and highlights the need for comprehensive security testing of font rendering libraries. Organizations should also review their overall security posture regarding file processing capabilities and ensure that input validation mechanisms are robust enough to handle malformed or malicious data without compromising system security.