CVE-2015-3679 in Mac OS X
Summary
by MITRE
Apple Type Services (ATS) in Apple OS X before 10.10.4 allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via a crafted font file, a different vulnerability than CVE-2015-3680, CVE-2015-3681, and CVE-2015-3682.
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Analysis
by VulDB Data Team • 05/22/2022
Apple Type Services represents a critical component within Apple's operating system that handles font processing and rendering across various applications and system interfaces. This vulnerability exists in OS X versions prior to 10.10.4 where the ATS framework fails to properly validate font data structures when processing maliciously crafted font files. The flaw manifests as a memory corruption issue that can be exploited by remote attackers who craft specially designed font files that, when processed by the system, trigger buffer overflows or other memory handling errors within the ATS subsystem.
The technical implementation of this vulnerability stems from inadequate input validation within the font parsing routines of Apple Type Services. When a malicious font file is loaded, the ATS component attempts to parse various font tables and metadata without sufficient bounds checking or sanitization. This allows an attacker to manipulate memory layout through crafted font data structures, potentially leading to arbitrary code execution within the context of the privileged system processes that handle font rendering. The vulnerability specifically affects the way ATS processes certain font format elements, particularly those related to font table structures and metadata handling.
The operational impact of this vulnerability extends beyond simple denial of service scenarios to encompass full system compromise capabilities. Attackers can leverage this weakness to execute arbitrary code on vulnerable systems, potentially gaining elevated privileges and establishing persistent access to affected machines. The remote exploitation capability means that adversaries can deliver malicious font files through various attack vectors including email attachments, web downloads, or compromised websites without requiring local system access. This makes the vulnerability particularly dangerous in enterprise environments where users may unknowingly interact with malicious content.
The vulnerability aligns with CWE-125, which describes out-of-bounds read conditions, and CWE-787, which covers out-of-bounds write operations, both of which are common in font parsing and rendering systems. From an ATT&CK framework perspective, this vulnerability maps to T1059.007 for application execution and T1190 for exploit public-facing application, as it enables remote code execution through font processing. The exploitation typically follows a pattern where attackers prepare malicious font files that trigger the memory corruption during normal system font processing operations, making the attack surface quite broad as font files are commonly encountered in various system contexts.
Mitigation strategies for this vulnerability primarily involve applying the official Apple security patches released as part of OS X 10.10.4 and subsequent updates. Organizations should implement comprehensive patch management processes to ensure all systems receive timely updates. Additional protective measures include implementing application whitelisting policies that restrict font file handling to trusted sources, disabling automatic font installation features, and monitoring for unusual font processing activities. Network-based protections can also be implemented through firewalls and content filtering systems that block suspicious font file types from entering the network perimeter. System administrators should also consider implementing sandboxing techniques that limit the privileges available to font processing components, thereby reducing the potential impact of successful exploitation attempts.