CVE-2017-2379 in tvOS
Summary
by MITRE
An issue was discovered in certain Apple products. iOS before 10.3 is affected. macOS before 10.12.4 is affected. tvOS before 10.2 is affected. watchOS before 3.2 is affected. The issue involves the "Carbon" component. It allows remote attackers to execute arbitrary code or cause a denial of service (buffer overflow and application crash) via a crafted .dfont file.
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Analysis
by VulDB Data Team • 11/21/2022
The vulnerability identified as CVE-2017-2379 represents a critical buffer overflow flaw within Apple's Carbon component system that affects multiple operating systems including iOS versions prior to 10.3, macOS versions before 10.12.4, tvOS versions before 10.2, and watchOS versions before 3.2. This issue stems from insufficient input validation mechanisms within the Carbon framework, which is a legacy application programming interface that provides core system services and graphics handling capabilities for Apple's platforms. The Carbon component serves as a bridge between applications and the underlying operating system, managing various system functions including font handling and graphics rendering operations.
The technical exploitation of this vulnerability occurs through the processing of maliciously crafted .dfont files, which are Apple's proprietary font format. When an application attempts to load or process these specially constructed font files, the buffer overflow condition manifests within the Carbon framework's font parsing routines. This flaw specifically affects how the system handles memory allocation during font file interpretation, where the application fails to properly validate the size and structure of the font data before attempting to copy it into fixed-size memory buffers. The insufficient bounds checking allows attackers to overflow these buffers and overwrite adjacent memory locations, potentially leading to arbitrary code execution or application crashes that result in denial of service conditions.
The operational impact of CVE-2017-2379 extends across Apple's ecosystem, affecting users of mobile devices, desktop computers, and embedded systems that rely on the Carbon framework for system operations. Attackers can remotely exploit this vulnerability by delivering malicious .dfont files through various attack vectors including email attachments, web downloads, or malicious websites that automatically attempt to render fonts in applications. The vulnerability's classification as a buffer overflow aligns with CWE-121, which specifically addresses stack-based buffer overflow conditions, and the potential for arbitrary code execution places this issue within the ATT&CK framework's technique T1059 for command and scripting interpreter and T1203 for Exploitation for Client Execution. The affected systems remain vulnerable even when users are not actively interacting with the malicious content, as the buffer overflow can occur during automatic font rendering processes in applications like web browsers, document viewers, or image editors.
Mitigation strategies for CVE-2017-2379 require immediate system updates to the affected Apple operating system versions, with the most effective approach being the installation of the corresponding security patches released by Apple. Users should prioritize updating their iOS devices to version 10.3 or later, macOS systems to version 10.12.4 or later, tvOS devices to version 10.2 or later, and watchOS devices to version 3.2 or later. Additionally, security administrators should implement network-based controls to block or scan for .dfont files from untrusted sources, particularly in enterprise environments where automated font processing might occur. The vulnerability demonstrates the importance of legacy component security management and highlights the risks associated with maintaining older frameworks that may not receive adequate security updates. Organizations should also consider implementing application whitelisting policies to restrict font file processing and reduce the attack surface for similar vulnerabilities in other system components.