CVE-2015-6978 in Mac OS X
Summary
by MITRE
FontParser in Apple iOS before 9.1 and OS X before 10.11.1 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-2015-6976, CVE-2015-6977, CVE-2015-6990, CVE-2015-6991, CVE-2015-6993, CVE-2015-7008, CVE-2015-7009, CVE-2015-7010, and CVE-2015-7018.
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Analysis
by VulDB Data Team • 11/19/2024
The vulnerability identified as CVE-2015-6978 represents a critical memory corruption flaw within Apple's FontParser component that affects iOS versions prior to 9.1 and OS X versions prior to 10.11.1. This vulnerability resides in the font parsing functionality that processes various font file formats including TrueType, OpenType, and other rasterization formats commonly used across Apple's operating systems. The flaw manifests when the system encounters malformed or specially crafted font files that exploit buffer overflows or improper memory handling during the parsing process, creating opportunities for remote code execution or system instability. The vulnerability operates at the kernel level where font rendering occurs, making it particularly dangerous as it can be triggered through various attack vectors including email attachments, web content, or malicious downloads.
The technical implementation of this vulnerability involves improper bounds checking and memory management within the font parsing routines that handle font file structures. When processing malformed font data, the FontParser fails to validate the integrity of font headers, table structures, or glyph data, leading to memory corruption that can be exploited to overwrite critical memory regions. This type of vulnerability aligns with CWE-121, heap-based buffer overflow, and CWE-122, stack-based buffer overflow, while also demonstrating characteristics of memory safety violations that enable arbitrary code execution. The attack surface expands significantly because font files are commonly encountered in various contexts including email attachments, web browsers, document viewers, and application installations, making this a high-value target for attackers seeking remote execution capabilities.
The operational impact of CVE-2015-6978 extends beyond simple denial of service scenarios to encompass full system compromise capabilities that align with ATT&CK technique T1059.007 for command and scripting interpreter. An attacker who successfully exploits this vulnerability can gain arbitrary code execution privileges on the target system, potentially leading to complete system compromise, data exfiltration, or deployment of additional malware. The vulnerability's remote exploitability means that attackers do not require physical access to the target device, making it particularly concerning for enterprise environments and mobile device management. Organizations running affected versions of Apple operating systems face significant risk exposure, as the vulnerability can be triggered through seemingly benign font files encountered in daily operations.
Mitigation strategies for CVE-2015-6978 primarily focus on immediate system updates to the patched versions of iOS 9.1 and OS X 10.11.1, which contain the necessary fixes for the FontParser memory handling routines. Network administrators should implement proactive patch management policies to ensure all affected devices receive updates promptly, while also considering network-level restrictions on font file types where possible. Security monitoring should include detection of unusual font file processing activities and potential exploitation attempts through network traffic analysis. The vulnerability highlights the importance of input validation and memory safety practices in system components that process untrusted data, reinforcing the need for defensive programming techniques and regular security assessments of core system libraries. Additionally, organizations should implement layered security approaches including email filtering, web content protection, and endpoint detection solutions to provide defense-in-depth against similar vulnerabilities that may exist in font processing components.