CVE-2015-3681 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-2015-3679, CVE-2015-3680, 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 rendering and processing for graphical user interfaces. This subsystem operates at a foundational level, processing font files to display text and graphics across various applications and system interfaces. The vulnerability exists within the font parsing mechanisms that process OpenType and TrueType font formats, which are extensively used throughout the macOS ecosystem. When ATS encounters malformed font data, it fails to properly validate input parameters, leading to memory corruption vulnerabilities that can be exploited by malicious actors.
The technical flaw manifests through improper bounds checking and memory management within the font processing pipeline. Attackers can craft specially designed font files that contain malformed data structures, specifically targeting buffer overflows and memory corruption patterns within the ATS subsystem. These crafted fonts exploit weaknesses in how the system handles font table parsing, particularly when processing complex font features such as ligatures, kerning tables, and advanced typographic controls. The vulnerability allows for arbitrary code execution when the system attempts to render these malicious fonts, as the corrupted memory can be manipulated to redirect program execution flow.
The operational impact of this vulnerability extends across multiple attack vectors and system components. Remote attackers can leverage this weakness through web browsers, email clients, or any application that processes font files, potentially executing malicious payloads without user interaction. The memory corruption can result in system crashes, application instability, or complete system compromise depending on the execution context. This vulnerability is particularly dangerous because font files are commonly encountered during normal system operation, making exploitation more likely and harder to prevent through traditional security measures. The attack surface includes not only direct application rendering but also system-level processes that handle font caching and preprocessing.
Mitigation strategies should focus on immediate system updates and enhanced input validation. Apple's release of OS X 10.10.4 addressed this vulnerability through improved font parsing routines and enhanced memory protection mechanisms. Organizations should implement comprehensive patch management protocols to ensure timely deployment of security updates. Additional defensive measures include restricting font file processing in untrusted environments, implementing sandboxing for font rendering components, and monitoring system logs for unusual font processing activities. The vulnerability aligns with CWE-125, which describes out-of-bounds read conditions, and CWE-787, which covers out-of-bounds write vulnerabilities, while potentially mapping to ATT&CK techniques involving privilege escalation and code execution through software supply chain attacks. Network administrators should also consider implementing web application firewalls and content filtering systems that can detect and block suspicious font file content to reduce the risk of exploitation.