CVE-2015-3694 in Mac OS X
Summary
by MITRE
FontParser in Apple iOS before 8.4 and 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-2015-3719.
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Analysis
by VulDB Data Team • 11/24/2024
The vulnerability identified as CVE-2015-3694 represents a critical memory corruption flaw within Apple's FontParser component that affected iOS versions prior to 8.4 and OS X versions prior to 10.10.4. This vulnerability resides in the font processing subsystem that handles various font file formats including TrueType, OpenType, and other rasterization formats used by Apple's operating systems. The flaw specifically manifests when the system attempts to parse maliciously crafted font files, creating a pathway for remote code execution or denial of service conditions. The vulnerability is particularly concerning because font files are commonly encountered in legitimate user workflows and web browsing scenarios, making exploitation relatively accessible to remote attackers. Security researchers have categorized this issue under CWE-125, which describes out-of-bounds read vulnerabilities, and it aligns with ATT&CK technique T1059.007 for process injection through legitimate system processes. The memory corruption occurs during font rendering operations when the parser fails to properly validate input parameters within font metadata structures, particularly affecting the handling of font table offsets and size calculations.
The technical exploitation of this vulnerability involves crafting a specially designed font file that contains malformed data structures which trigger buffer overflows or memory corruption when processed by Apple's font rendering engine. Attackers can deliver these malicious font files through various vectors including email attachments, web pages, or malicious websites that automatically attempt to render the font within the browser or system environment. When the vulnerable system processes such a font file, the corrupted memory state can lead to arbitrary code execution with the privileges of the rendering process, typically running with elevated system permissions. The vulnerability's impact extends beyond simple code execution to include potential system crashes, application instability, and complete system compromise depending on the execution context and privilege level of the affected process. The flaw demonstrates how seemingly benign components like font parsers can serve as attack surfaces for sophisticated exploitation techniques, particularly when dealing with complex file format parsing that involves multiple layers of data validation and memory management.
From an operational perspective, this vulnerability creates significant risk for organizations relying on Apple devices as it allows attackers to gain unauthorized access to systems through indirect means. The remote nature of the attack vector means that users need not interact with malicious content directly for exploitation to occur, as automatic font rendering occurs during normal browsing or document processing activities. Organizations should consider this vulnerability as part of broader mobile device management strategies, particularly in environments where iOS devices are prevalent. The vulnerability affects not only end-user devices but also enterprise systems that may process font files from external sources or host web content that could be exploited. Security teams must implement comprehensive monitoring for suspicious font file handling activities and ensure timely patch deployment across all affected systems. This vulnerability highlights the importance of maintaining up-to-date system patches and demonstrates how vulnerabilities in system libraries can have cascading effects across multiple operating system components. The impact assessment should include consideration of potential lateral movement capabilities if exploitation succeeds, as well as the possibility of using this vulnerability as a stepping stone for more advanced attacks within a network environment.
Mitigation strategies for CVE-2015-3694 should include immediate deployment of Apple's security updates for iOS 8.4 and OS X 10.10.4, which address the underlying memory corruption issues in the FontParser component. Organizations should implement network-based controls to block or scan font file attachments and embedded font content in web traffic, particularly in high-risk environments. System administrators should consider disabling automatic font rendering in web browsers and email clients where possible, and implement strict content filtering policies for font files from untrusted sources. Additionally, security monitoring should be enhanced to detect unusual font processing activities that may indicate exploitation attempts. The vulnerability underscores the importance of regular vulnerability assessments and security audits focusing on system libraries and components that handle untrusted input data. Organizations should also consider implementing application whitelisting policies to restrict font processing to trusted applications only, and maintain detailed logging of font file processing activities for forensic analysis purposes. These measures align with security best practices outlined in NIST SP 800-53 and ISO 27001 frameworks for managing software vulnerabilities and protecting against memory corruption attacks.