CVE-2015-6992 in Mac OS X
Summary
by MITRE
CoreText in Apple iOS before 9.1, OS X before 10.11.1, and iTunes before 12.3.1 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-2015-6975 and CVE-2015-7017.
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Analysis
by VulDB Data Team • 06/24/2022
The vulnerability identified as CVE-2015-6992 represents a critical memory corruption flaw within Apple's CoreText framework that affected multiple operating systems including iOS versions prior to 9.1, macOS versions before 10.11.1, and iTunes versions before 12.3.1. This vulnerability operates through a sophisticated attack vector involving crafted font files that can be delivered remotely, making it particularly dangerous for widespread exploitation. The CoreText framework serves as a fundamental component responsible for text rendering across Apple's ecosystem, handling font processing and text layout operations that are integral to user interface rendering and document processing. The flaw specifically manifests when the system processes maliciously constructed font files that contain malformed data structures or unexpected memory layouts that can trigger buffer overflows or memory corruption conditions within the CoreText processing pipeline.
The technical implementation of this vulnerability leverages the way CoreText handles font file parsing and memory allocation during text rendering operations. When a malicious font file is processed, the framework's font parser fails to properly validate the structure and boundaries of font data, particularly in how it handles certain font table formats and metadata. This inadequate validation allows attackers to craft font files containing specially constructed data that, when processed by CoreText, results in memory corruption. The vulnerability falls under the CWE-121 category of stack-based buffer overflow and CWE-125 out-of-bounds read conditions, as the memory corruption occurs during font data processing rather than during direct memory manipulation. The attack can be executed remotely through various delivery mechanisms including email attachments, web pages, or file downloads, making it a significant threat vector for social engineering campaigns. The exploitation can result in either arbitrary code execution or denial of service conditions, where the system becomes unstable and crashes, potentially leading to complete system compromise.
The operational impact of CVE-2015-6992 extends beyond simple system instability to encompass serious security implications for enterprise and individual users alike. The vulnerability's ability to execute arbitrary code remotely makes it particularly dangerous for targeted attacks against high-value targets including corporate executives, government officials, or security researchers. The memory corruption can be leveraged to gain elevated privileges, install persistent backdoors, or exfiltrate sensitive data from affected systems. In enterprise environments, this vulnerability could enable attackers to establish footholds within networks, particularly in scenarios where users might encounter malicious font files through legitimate business processes such as document sharing or email communication. The vulnerability's presence across multiple Apple platforms including mobile devices, desktop operating systems, and desktop applications creates a wide attack surface that increases the likelihood of successful exploitation. Organizations using affected versions of Apple software face potential data breaches, system compromise, and disruption of business operations, with the vulnerability being classified as a critical threat in security assessment frameworks.
Mitigation strategies for CVE-2015-6992 primarily focus on immediate patch deployment and system hardening measures to reduce attack surface exposure. Apple's official remediation involves updating to iOS 9.1, macOS 10.11.1, or iTunes 12.3.1, which contain patches that address the font parsing validation issues within CoreText. Security administrators should implement comprehensive patch management protocols to ensure all affected systems receive updates promptly, particularly in enterprise environments where multiple devices may be vulnerable. Additional defensive measures include implementing email filtering and web content filtering solutions that can identify and block potentially malicious font files, as well as monitoring network traffic for suspicious font file transfers. The vulnerability's characteristics align with ATT&CK technique T1059.007 for application execution through font files, and T1070.004 for file and directory permissions modification that may occur during exploitation. Organizations should also consider implementing sandboxing mechanisms and privilege separation to limit the potential impact of successful exploitation, as well as establishing incident response procedures specifically designed to handle memory corruption vulnerabilities. Network segmentation and user access controls can further reduce the risk of lateral movement if an attacker successfully exploits this vulnerability on a single endpoint.